C++ 代码

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
using namespace std;
const int  N = 510;

int g[N][N], dist[N], n, m;
bool st[N];

int dijkstra()
{
    //每个点初始为正无穷
    memset(dist, 0x3f, sizeof dist);
    //一号点初始距离为0
    dist[1] = 0;
    for(int i = 1; i <= n; i++)
    {
        int t = -1;
        for(int j = 1; j <= n; j ++)
            //每次取出离1号点最近的点
            if(!st[j] && (t == -1 || dist[t] > dist[j]))
                t = j;

        //将这个离一最近的点改变st状态
        st[t] = true;

        //将这个点与其他相连点更新距离
        for(int j = 1; j <= n; j++)
            dist[j] = min(dist[j], dist[t] + g[t][j]);
    }
    if(dist[n] == 0x3f3f3f3f) return -1;
    else return dist[n];
}



int main()
{
    cin.tie(0);
    cin >> n >> m;
    int a, b, c;

    memset(g, 0x3f, sizeof g);
    while(m--)
    {
        cin >> a >> b >> c;

        //这样可以处理自环，重边
        g[a][b] = min(g[a][b], c);
    }

    int t = dijkstra();
    cout << t;
}