最短路

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
#include <cmath>
#include <map>
#include <stack>
#include <vector>
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
using namespace std;

const int MX=110;
const int INF=0x3f3f3f3f;

int n,Map[MX][MX],dist[MX];
void init(){
    for (int i=1;i<=n;i++)
        for (int j=1;j<=n;j++)
            Map[i][j]=INF;
}
void dijkstra(int v0){
    bool S[MX];
    for (int i=1;i<=n;i++){             //初始化
        dist[i]=Map[v0][i];
        S[i]=false;
    }
    dist[v0]=0;
    S[v0]=true;
    for (int i=2;i<=n;i++){
        int temp=INF;
        int u=v0;
        for (int j=1;j<=n;j++)          //找出距离v0最小的点
            if (!S[j]&&dist[j]<temp){
                u=j;
                temp=dist[j];
            }
        S[u]=true;
        for (int j=1;j<=n;j++)          //判断
            if (!S[j]&&dist[u]+Map[u][j]<dist[j])
                dist[j]=dist[u]+Map[u][j];
    }
}
int main()
{
    int m;
    while (~scanf ("%d %d",&n,&m)){
        if (n==0&m==0) break;
        init();
        while (m--){
            int u,v,w;
            scanf ("%d %d %d",&u,&v,&w);
            if (Map[u][v]==INF){
                Map[u][v]=w;
                Map[v][u]=w;
            }
        }
        dijkstra(1);
        printf ("%d\n",dist[n]);        //如果dist[n]等于INF，说明1到n之间不可达
    }
    return 0;
}