Dijkstra算法简单实现（C++）

图的最短路径问题主要包括三种算法：

（3）Bellman (含有负权边的单源最短路径）

本文主要讲使用C++实现简单的Dijkstra算法

Dijkstra算法简单实现（C++）

  1 #include<iostream>
  2 #include<stack>
  3 using namespace std;
  4 
  5 #define MAXVEX 9
  6 #define INFINITY 65535
  7 
  8 typedef int Patharc[MAXVEX];
  9 typedef int ShortPathTable[MAXVEX];
 10 
 11 typedef struct {
 12     int vex[MAXVEX];
 13     int arc[MAXVEX][MAXVEX];
 14     int numVertexes;
 15 } MGraph;
 16 
 17 // 构建图
 18 void CreateMGraph(MGraph *G){
 19     int i, j, k;
 20     // 初始化图
 21     G->numVertexes = 9;
 22     for(i = 0; i < G->numVertexes; ++i){
 23         G->vex[i] = i;
 24     }
 25     for(i = 0; i < G->numVertexes; ++i){
 26         for(j = 0; j < G->numVertexes; ++j){
 27             if(i == j)
 28                 G->arc[i][j] = 0;
 29             else
 30                 G->arc[i][j] = G->arc[j][i] = INFINITY;
 31         }
 32     }
 33 
 34     G->arc[0][1] = 1;
 35     G->arc[0][2] = 5;
 36 
 37     G->arc[1][2] = 3;
 38     G->arc[1][3] = 7;
 39     G->arc[1][4] = 5;
 40 
 41     G->arc[2][4] = 1;
 42     G->arc[2][5] = 7;
 43 
 44     G->arc[3][4] = 2;
 45     G->arc[3][6] = 3;
 46 
 47     G->arc[4][5] = 3;
 48     G->arc[4][6] = 6;
 49     G->arc[4][7] = 9;
 50 
 51     G->arc[5][7] = 5;
 52 
 53     G->arc[6][7] = 2;
 54     G->arc[6][8] = 7;
 55 
 56     G->arc[7][8] = 4;
 57 
 58     // 设置对称位置元素值
 59     for(i = 0; i < G->numVertexes; ++i){
 60         for(j = i; j < G->numVertexes; ++j){
 61             G->arc[j][i] = G->arc[i][j];
 62         }
 63     }
 64 }
 65 
 66 void ShortPath_Dijkstra(MGraph G, int v0, Patharc P, ShortPathTable D){
 67     int final[MAXVEX];
 68     int i;
 69     for(i = 0; i < G.numVertexes; ++i){
 70         final[i] = 0;
 71         D[i] = G.arc[v0][i];
 72         P[i] = 0;
 73     }
 74     D[v0] = 0;
 75     final[v0] = 1;
 76     for(i = 0; i < G.numVertexes; ++i){
 77         int min = INFINITY;
 78         int j, k, w;
 79 
 80         for(j = 0; j < G.numVertexes; ++j){// 查找距离V0最近的顶点
 81             if(!final[j] && D[j] < min){
 82                 k = j;
 83                 min = D[j];
 84             }
 85         }
 86         final[k] = 1;
 87         for(w = 0; w < G.numVertexes; ++w){// 更新各个顶点的距离
 88             if(!final[w] && (min + G.arc[k][w]) < D[w]){
 89                 D[w] = min + G.arc[k][w];
 90                 P[w] = k;
 91             }
 92         }
 93     }
 94 }
 95 
 96 // 打印最短路径
 97 void PrintShortPath(MGraph G, int v0, Patharc P, ShortPathTable D){
 98     int i, k;
 99     stack<int> path;
100     cout<<"顶点v"<<v0<<"到其他顶点之间的最短路径如下: "<<endl;
101     for(i = 0; i < G.numVertexes; ++i){
102         if(i == v0) continue;
103         cout<<"v"<<v0<<"--"<<"v"<<i<<" weight: "<<D[i]<<"  Shortest path: ";
104         path.push(i);
105         int k = P[i];
106         while(k != 0){
107             path.push(k);
108             k = P[k];
109         }
110         path.push(v0);
111         while(!path.empty()){
112             if(path.size() != 1)
113                 cout<<path.top()<<"->";
114             else
115                 cout<<path.top()<<endl;
116             path.pop();
117         }
118     }
119 }
120 
121 int main(int argc, char const *argv[]) {
122     int v0 = 0; // 源点
123     MGraph G;
124     Patharc P;
125     ShortPathTable D;
126     CreateMGraph(&G);
127     ShortPath_Dijkstra(G, v0, P, D);
128     PrintShortPath(G, v0, P, D);
129     return 0;
130 }

运行结果

顶点v0到其他顶点之间的最短路径如下: 
v0--v1 weight: 1  Shortest path: 0->1
v0--v2 weight: 4  Shortest path: 0->1->2
v0--v3 weight: 7  Shortest path: 0->1->2->4->3
v0--v4 weight: 5  Shortest path: 0->1->2->4
v0--v5 weight: 8  Shortest path: 0->1->2->4->5
v0--v6 weight: 10  Shortest path: 0->1->2->4->3->6
v0--v7 weight: 12  Shortest path: 0->1->2->4->3->6->7
v0--v8 weight: 16  Shortest path: 0->1->2->4->3->6->7->8
[Finished in 1.8s]