dijsktra

#include <bits/stdc++.h>

using namespace std;

const int N = 510;

int g[N][N], n, m;

int dist[N];
bool st[N];

int dijsktra()
{
    memset(dist, 0x3f, sizeof dist);
    dist[1] = 0;
    
    for(int i = 1; i < n; i ++)
    {
        int t = -1;
        for(int j = 1; j <= n; j ++)
            if(!st[j] && (t == -1 || dist[t] >= dist[j]))
                t = j;
        
        for(int j = 1; j <= n; j ++)
            dist[j] = min(dist[j], dist[t] + g[t][j]);
            
        st[t] = 1;
    }
    
    return (dist[n] == 0x3f3f3f3f ? -1 : dist[n]);
}

int main()
{
    memset(g, 0x3f, sizeof g);
    
    cin >> n >> m;
    
    for(int i = 1; i <= m; i ++)
    {
        int a, b, c;
        cin >> a >> b >>c;
        g[a][b] = min(g[a][b], c);
    }
    
    cout << dijsktra();
}