最短路径 一 Dijkstra 模板(O(n^2))

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

#include<iostream>
#include<cstdio>
#include<cstring>
#define INF 0x03F3F3F3F
#define N 1024
int path[N], vis[N];
int cost[N][N],lowcost[N];
void Dijkstra(int n, int beg){
 int i, j, min;
 memset(vis, 0, sizeof(vis));
 vis[beg] = 1;
 for (i=0; i<n; i++)
{
  lowcost[i] = cost[beg][i]; path[i] = beg;
}
lowcost[beg] = 0;
path[beg] = -1;   //
int pre = beg;
for (i=1; i<n; i++){
    min = INF;
    for (j=0; j<n; j++)
        if (vis[j]==0 && lowcost[pre]+cost[pre][j]<lowcost[j])
        {
        lowcost[j] = lowcost[pre] + cost[pre][j];
        path[j] = pre;
        }
    for (j=0; j<n; j++)
        if (vis[j] == 0 && lowcost[j] < min){
                min = lowcost[j]; pre = j;
        }
    vis[pre] = 1;
 }
}
int main(){
    int n,m,s,t,i,k,a,b,c;
    scanf("%d%d%d%d",&n,&m,&s,&t);
    memset(cost,INF,sizeof(cost));
    for(i = 0 ;i<m;i++){
        scanf("%d%d%d",&a,&b,&c);
        if(c<cost[a-1][b-1]){
            cost[a-1][b-1] = c;
            cost[b-1][a-1] = c;
        }
    }
    Dijkstra(n, s-1);
    printf("%d
",lowcost[t-1]);
    return 0;
}