深度优先搜索与广度优先搜索
版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。
广度优先搜索（宽度优先搜索，BFS）和深度优先搜索（DFS）算法的应用非常广泛，本篇文章主要介绍BFS与DFS的原理、实现和应用。
深度优先搜索
图的深度优先搜索(Depth First Search)，和树的先序遍历比较类似。
它的思想：假设初始状态是图中所有顶点均未被访问，则从某个顶点v出发，首先访问该顶点，然后依次从它的各个未被访问的邻接点出发深度优先搜索遍历图，直至图中所有和v有路径相通的顶点都被访问到。 若此时尚有其他顶点未被访问到，则另选一个未被访问的顶点作起始点，重复上述过程，直至图中所有顶点都被访问到为止。
显然，深度优先搜索是一个递归的过程。
下面进行说明：
第1步：访问A。
第2步：访问(A的邻接点)C。在第1步访问A之后，接下来应该访问的是A的邻接点，即"C,D,F"中的一个。但在本文的实现中，顶点ABCDEFG是按照顺序存储，C在"D和F"的前面，因此，先访问C。
第3步：访问(C的邻接点)B。在第2步访问C之后，接下来应该访问C的邻接点，即"B和D"中一个(A已经被访问过，就不算在内)。而由于B在D之前，先访问B。
第4步：访问(C的邻接点)D。在第3步访问了C的邻接点B之后，B没有未被访问的邻接点；因此，返回到访问C的另一个邻接点D。
第5步：访问(A的邻接点)F。 前面已经访问了A，并且访问完了"A的邻接点B的所有邻接点(包括递归的邻接点在内)"；因此，此时返回到访问A的另一个邻接点F。
第6步：访问(F的邻接点)G。
第7步：访问(G的邻接点)E。
因此访问顺序是：A -> C -> B -> D -> F -> G -> E。
当然，上图是基于无向图，具体的代码在文章后面实现。
广度优先搜索
广度优先搜索算法(Breadth First Search)，又称为"宽度优先搜索"或"横向优先搜索"，简称BFS。
它的思想是：从图中某顶点v出发，在访问了v之后依次访问v的各个未曾访问过的邻接点，然后分别从这些邻接点出发依次访问它们的邻接点，并使得“先被访问的顶点的邻接点先于后被访问的顶点的邻接点被访问，直至图中所有已被访问的顶点的邻接点都被访问到。如果此时图中尚有顶点未被访问，则需要另选一个未曾被访问过的顶点作为新的起始点，重复上述过程，直至图中所有顶点都被访问到为止。
换句话说，广度优先搜索遍历图的过程是以v为起点，由近至远，依次访问和v有路径相通且路径长度为1,2…的顶点。
第1步：访问A。
第2步：依次访问C,D,F。在访问了A之后，接下来访问A的邻接点。前面已经说过，在本文实现中，顶点ABCDEFG按照顺序存储的，C在"D和F"的前面，因此，先访问C。再访问完C之后，再依次访问D,F。
第3步：依次访问B,G。在第2步访问完C,D,F之后，再依次访问它们的邻接点。首先访问C的邻接点B，再访问F的邻接点G。
第4步：访问E。在第3步访问完B,G之后，再依次访问它们的邻接点。只有G有邻接点E，因此访问G的邻接点E。
因此访问顺序是：A -> C -> D -> F -> B -> G -> E。
代码实现
我们以以下无向图来进行测试：
存储顺序为A->B->C->D->E.
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;
public class DFSAndBFS {
<span class="token comment">//初始化顶点个数，当然也可以自己写一个函数由用户输入自定义图，这里重点不是图的构造</span>
<span class="token keyword">private</span> <span class="token keyword">int</span> numVertexes <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span>
<span class="token comment">//初始化顶点</span>
<span class="token keyword">private</span> String<span class="token punctuation">[</span><span class="token punctuation">]</span> vex<span class="token punctuation">;</span>
<span class="token comment">//邻接矩阵，表明了顶点的关系</span>
<span class="token keyword">private</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span> acr<span class="token punctuation">;</span>
<span class="token keyword">private</span> <span class="token function">DFSAndBFS</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
vex<span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">{</span><span class="token string">"A"</span><span class="token punctuation">,</span> <span class="token string">"B"</span><span class="token punctuation">,</span> <span class="token string">"C"</span><span class="token punctuation">,</span> <span class="token string">"D"</span><span class="token punctuation">,</span> <span class="token string">"E"</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
acr<span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">{</span>
<span class="token punctuation">{</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token punctuation">{</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token punctuation">{</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">}</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">printGraph</span><span class="token punctuation">(</span>DFSAndBFS g<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"图中各顶点的关系如下图所示（邻接矩阵，1代表两顶点有边，0代表无）"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span><span class="token string">" "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>i<span class="token operator"><</span>g<span class="token punctuation">.</span>numVertexes<span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>vex<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">+</span><span class="token string">" "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>i<span class="token operator"><</span>g<span class="token punctuation">.</span>numVertexes<span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>vex<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">+</span><span class="token string">" "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> j<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>j<span class="token operator"><</span>g<span class="token punctuation">.</span>numVertexes<span class="token punctuation">;</span>j<span class="token operator">++</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>acr<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">+</span><span class="token string">" "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token comment">//深度优先遍历，递归算法</span>
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">DFSTraverse</span><span class="token punctuation">(</span>DFSAndBFS g<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token comment">//建立访问数组</span>
<span class="token keyword">boolean</span> <span class="token punctuation">[</span><span class="token punctuation">]</span>visited<span class="token operator">=</span><span class="token keyword">new</span> <span class="token class-name">boolean</span> <span class="token punctuation">[</span>g<span class="token punctuation">.</span>numVertexes<span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token comment">//初始化 访问顶点</span>
<span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>i<span class="token operator"><</span>visited<span class="token punctuation">.</span>length<span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span>
visited<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">=</span><span class="token boolean">false</span><span class="token punctuation">;</span>
<span class="token comment">//对未访问顶点调用DFS</span>
<span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>i<span class="token operator"><</span>visited<span class="token punctuation">.</span>length<span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token operator">!</span>visited<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span>
<span class="token function">DFS</span><span class="token punctuation">(</span>g<span class="token punctuation">,</span>i<span class="token punctuation">,</span>visited<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token comment">//从顶点i开始进行的深度优先搜索DFS</span>
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">DFS</span><span class="token punctuation">(</span>DFSAndBFS g<span class="token punctuation">,</span> <span class="token keyword">int</span> i<span class="token punctuation">,</span> <span class="token keyword">boolean</span><span class="token punctuation">[</span><span class="token punctuation">]</span> visited<span class="token punctuation">)</span> <span class="token punctuation">{</span>
visited<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">=</span><span class="token boolean">true</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>vex<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">+</span><span class="token string">" "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> j<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>j<span class="token operator"><</span>g<span class="token punctuation">.</span>numVertexes<span class="token punctuation">;</span>j<span class="token operator">++</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token keyword">if</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>acr<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">></span><span class="token number">0</span> <span class="token operator">&&</span> <span class="token operator">!</span>visited<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">)</span>
<span class="token function">DFS</span><span class="token punctuation">(</span>g<span class="token punctuation">,</span>j<span class="token punctuation">,</span>visited<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token comment">//深度优先遍历，非递归算法</span>
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">DFS</span><span class="token punctuation">(</span>DFSAndBFS g<span class="token punctuation">)</span><span class="token punctuation">{</span>
<span class="token keyword">boolean</span><span class="token punctuation">[</span><span class="token punctuation">]</span> visited <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">boolean</span><span class="token punctuation">[</span>numVertexes<span class="token punctuation">]</span><span class="token punctuation">;</span>
Stack<span class="token generics function"><span class="token punctuation"><</span>Integer<span class="token punctuation">></span></span> stack <span class="token operator">=</span><span class="token keyword">new</span> <span class="token class-name">Stack</span><span class="token generics function"><span class="token punctuation"><</span>Integer<span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>i<span class="token operator"><</span>g<span class="token punctuation">.</span>numVertexes<span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token operator">!</span>visited<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
visited<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">=</span><span class="token boolean">true</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>vex<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">+</span><span class="token string">" "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
stack<span class="token punctuation">.</span><span class="token function">push</span><span class="token punctuation">(</span>i<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">while</span><span class="token punctuation">(</span><span class="token operator">!</span>stack<span class="token punctuation">.</span><span class="token function">isEmpty</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
<span class="token keyword">int</span> k <span class="token operator">=</span> stack<span class="token punctuation">.</span><span class="token function">pop</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> j<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>j<span class="token operator"><</span>g<span class="token punctuation">.</span>numVertexes<span class="token punctuation">;</span>j<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
<span class="token keyword">if</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>acr<span class="token punctuation">[</span>k<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">==</span><span class="token number">1</span><span class="token operator">&&</span> <span class="token operator">!</span>visited<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
visited<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">=</span><span class="token boolean">true</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>vex<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">+</span><span class="token string">" "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
stack<span class="token punctuation">.</span><span class="token function">push</span><span class="token punctuation">(</span>j<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">break</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token comment">//广度优先搜索</span>
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">BFS</span><span class="token punctuation">(</span>DFSAndBFS g<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token keyword">int</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>
Queue<span class="token generics function"><span class="token punctuation"><</span>Integer<span class="token punctuation">></span></span> q<span class="token operator">=</span><span class="token keyword">new</span> <span class="token class-name">LinkedList</span><span class="token generics function"><span class="token punctuation"><</span>Integer<span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">//建立访问数组</span>
<span class="token keyword">boolean</span> visited<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token operator">=</span><span class="token keyword">new</span> <span class="token class-name">boolean</span><span class="token punctuation">[</span>numVertexes<span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token comment">//初始化 访问顶点</span>
<span class="token keyword">for</span><span class="token punctuation">(</span>i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>i<span class="token operator"><</span>g<span class="token punctuation">.</span>numVertexes<span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span>
visited<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">=</span><span class="token boolean">false</span><span class="token punctuation">;</span>
<span class="token comment">//对每个顶点做循环</span>
<span class="token keyword">for</span><span class="token punctuation">(</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>i<span class="token operator"><</span>g<span class="token punctuation">.</span>numVertexes<span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token operator">!</span>visited<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
visited<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">=</span><span class="token boolean">true</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>vex<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">+</span><span class="token string">" "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
q<span class="token punctuation">.</span><span class="token function">offer</span><span class="token punctuation">(</span>i<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">while</span><span class="token punctuation">(</span><span class="token operator">!</span>q<span class="token punctuation">.</span><span class="token function">isEmpty</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
i<span class="token operator">=</span>q<span class="token punctuation">.</span><span class="token function">poll</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> j<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>j<span class="token operator"><</span>g<span class="token punctuation">.</span>numVertexes<span class="token punctuation">;</span>j<span class="token operator">++</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token keyword">if</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>acr<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">></span><span class="token number">0</span> <span class="token operator">&&</span> <span class="token operator">!</span>visited<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
visited<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">=</span><span class="token boolean">true</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>g<span class="token punctuation">.</span>vex<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">+</span><span class="token string">" "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
q<span class="token punctuation">.</span><span class="token function">offer</span><span class="token punctuation">(</span>j<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String <span class="token punctuation">[</span><span class="token punctuation">]</span>args<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
DFSAndBFS g<span class="token operator">=</span><span class="token keyword">new</span> <span class="token class-name">DFSAndBFS</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
g<span class="token punctuation">.</span><span class="token function">printGraph</span><span class="token punctuation">(</span>g<span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"深度优先搜索(递归)结果："</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
g<span class="token punctuation">.</span><span class="token function">DFSTraverse</span><span class="token punctuation">(</span>g<span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"深度优先搜索(非递归)结果："</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
g<span class="token punctuation">.</span><span class="token function">DFS</span><span class="token punctuation">(</span>g<span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"广度优先搜索结果："</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
g<span class="token punctuation">.</span><span class="token function">BFS</span><span class="token punctuation">(</span>g<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
- 118
- 119
- 120
- 121
- 122
- 123
- 124
- 125
- 126
- 127
- 128
- 129
- 130
- 131
- 132
- 133
- 134
- 135
- 136
- 137
- 138
- 139
- 140
- 141
- 142
- 143
- 144
- 145
- 146
- 147
- 148
- 149
- 150
- 151
- 152
- 153
- 154
- 155
- 156
- 157
- 158
- 159
测试结果：
图中各顶点的关系如下图所示（邻接矩阵，1代表两顶点有边，0代表无）
A B C D E
A 0 1 0 1 0
B 1 0 1 0 0
C 0 1 0 0 1
D 1 0 1 0 0
E 0 0 1 0 0
深度优先搜索(递归)结果：
A B C E D
深度优先搜索(非递归)结果：
A B C E D
广度优先搜索结果：
A B D C E
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
以上就是本篇文章讲述的DFS与BFS了，还有一些基于树去做DFS和BFS的，当然我们的树也可以转化为图的。推荐一篇关于树的DFS于BFS。如链接：https://www.cnblogs.com/xiaolovewei/p/7763867.html。
如果您有什么疑问、想法或者建议都可以联系我哦。联系方式:cxylingfeng@foxmail.com发送邮件。
转载或者引用内容请注明出处。
喜欢本文的朋友们，欢迎长按下图二维码并关注订阅号程序员凌风，收看更多精彩的文章。
</div>
<link href="https://csdnimg.cn/release/phoenix/mdeditor/markdown_views-095d4a0b23.css" rel="stylesheet">
</div>
