Dijkstra求最短路 I

#include<bits/stdc++.h>
using namespace std;
const int N = 510, M = 1e5 + 10;
int n, m;
int dist[N];//存储每个点到1号点的最短距离
bool st[N];//表示每个点的最短路是否确定
int g[N][N];//稀疏图，用邻接矩阵存储

int dijkstra()
{
    memset(dist, 0x3f, sizeof dist);
    dist[1] = 0;
    
    for(int i = 1; i <= n; i ++)
    {
        int t = -1;
        //依次找到距离1号点最近的点
        for(int j = 1; j <= n; j ++)
        {
            if(!st[j] &&(t == -1 || dist[j] < dist[t]))
            {
                t = j;
            }
        }
        
        st[t] = true;
        
        //用刚找到的点更新其它点到1号点的距离
        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 >> n >> m;
    memset(g, 0x3f, sizeof g);
    while (m -- ){
        int a, b, c;
        cin >> a >> b >> c;
        g[a][b] = min(g[a][b], c);
    }
    
    int t = dijkstra();
    cout << t << endl;
}