最短路径 一 Dijkstra 模板(O(n^2))

题目传送：http://hihocoder.com/problemset/problem/1081

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #define INF 0x03F3F3F3F
 5 #define N 1024
 6 int path[N], vis[N];
 7 int cost[N][N],lowcost[N];
 8 void Dijkstra(int n, int beg){
 9  int i, j, min;
10  memset(vis, 0, sizeof(vis));
11  vis[beg] = 1;
12  for (i=0; i<n; i++)
13 {
14   lowcost[i] = cost[beg][i]; path[i] = beg;
15 }
16 lowcost[beg] = 0;
17 path[beg] = -1;   //
18 int pre = beg;
19 for (i=1; i<n; i++){
20     min = INF;
21     for (j=0; j<n; j++)
22         if (vis[j]==0 && lowcost[pre]+cost[pre][j]<lowcost[j])
23         {
24         lowcost[j] = lowcost[pre] + cost[pre][j];
25         path[j] = pre;
26         }
27     for (j=0; j<n; j++)
28         if (vis[j] == 0 && lowcost[j] < min){
29                 min = lowcost[j]; pre = j;
30         }
31     vis[pre] = 1;
32  }
33 }
34 int main(){
35     int n,m,s,t,i,k,a,b,c;
36     scanf("%d%d%d%d",&n,&m,&s,&t);
37     memset(cost,INF,sizeof(cost));
38     for(i = 0 ;i<m;i++){
39         scanf("%d%d%d",&a,&b,&c);
40         if(c<cost[a-1][b-1]){
41             cost[a-1][b-1] = c;
42             cost[b-1][a-1] = c;
43         }
44     }
45     Dijkstra(n, s-1);
46     printf("%d\n",lowcost[t-1]);
47     return 0;
48 }