Dijkstra algorithm for finding the shortest path

Given a point n and m edges directed graph, there may be multiple edges in FIG loopback and all are positive edge weights.

Please find the shortest distance from point 1 to point number n, n number if you can not go from point 1 point, then output -1.

Input Format

The first line contains the integers n and m.

Next m lines contains three integers x, y, Z, represents between points x and y point to have an edge side length z.

Output Format

Output an integer, represents the shortest distance to the point 1 point number n.

If the path does not exist, the output of -1.

data range

. 1 ≤ n- ≤ 500 1≤n≤500,
. 1 ≤ m ≤ 10 . 5 1≤m≤105,
FIG relates to a side not more than 10,000.

Sample input:

3 3
1 2 2
2 3 1
1 3 4

Sample output:

3

#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=510;
int dis[N],g[N][N],m,n;
bool st[N];
int dijkstra(){
    memset(dis,0x3f,sizeof(dis));
    dis[1]=0;
    for(int i=0;i<n;i++){
        int t=-1;
        for(int j=1;j<=n;j++){
            if(!st[j]&&(t==-1||dis[t]>dis[j]))
                t=j;
        }
        st[t]=true;
        for(int j=1;j<=n;j++){
            dis[j]=min(dis[j],dis[t]+g[t][j]);
        }
    }
    if(dis[n]==0x3f3f3f3f)return -1;
    return dis[n];
}
int main(void){
    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);
    }
    cout<<dijkstra()<<endl;
    return 0;
}