《算法导论》习题解答 Chapter 22.1-3（转置图）

一、邻接表实现

思路：一边遍历，一边倒置边，并添加到新的图中

邻接表实现伪代码：

for each u 属于 Vertex
	for v 属于 Adj[u]
		Adj1[v].insert(u);

复杂度：O(V+E);

输入：

3 3
a b
b c
c a

源代码：

package C22;

import java.util.Iterator;

public class C1_3{

	public static Adjacent_List getTransposeGraph(Adjacent_List g){
		Adjacent_List Gt = new Adjacent_List(g.getSize());
		for(int u=0;u<g.getSize();u++){
			Iterator<String> iter = g.getListByVertexIndex(u).iterator();
			while(iter.hasNext()){
				String vstr = iter.next();
				Gt.addEdge(vstr , g.getVertexValue(u));	//添加导致边
			}
		}
		return Gt;
	}
	public static void main(String[] args) throws Exception {
		Adjacent_List adjlist = GraphFactory.getAdjacentListInstance("input\\transpose_input.txt");
		System.out.println("====原图===");
		adjlist.printAllEdges();
		Adjacent_List transposeGraph = getTransposeGraph(adjlist);
		System.out.println("=====倒置图=====");
		transposeGraph.printAllEdges();
	}
}

二、邻接矩阵实现


思路：遍历二维数组，并A'[i][j] = A[j][i];

伪代码：

for i = 1 to V
	for j = 1 to V
		A'[j][i] = A[i][j];

复杂度：O(V^2);

源代码：

package C22;

import java.util.Iterator;

public class C1_3{

	public static Adjacent_Matrix getTransposeMatrix(Adjacent_Matrix g){
		Adjacent_Matrix Gt = new Adjacent_Matrix(g.getSize());
		for(int i=0;i<g.getSize();i++){
			for(int j=0;j<g.getSize();j++){
				Gt.setEdge(g.getVertexValue(j), g.getVertexValue(i), g.getElement(i, j));
			}
		}
		return Gt;
	}
	public static void main(String[] args) throws Exception {
		Adjacent_Matrix adj_matrix = GraphFactory.getAdjacentMatrixInstance("input\\transpose_input.txt");
		adj_matrix.printAllEdges();
		System.out.println("================");
		Adjacent_Matrix Gt = getTransposeMatrix(adj_matrix);
		Gt.printAllEdges();
	}
}

（原文点此，索引目录。感谢xiazdong君 && Google酱。这里是偶尔做做搬运工的水果君(^_^) ）