dijkstra(朴素版)

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 510;

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

int dijkstra()
{
    memset(dist, 0x3f, sizeof dist);

    dist[1] = 0;

    for (int i = 0; i < n - 1; 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] = true;

    }

    if (dist[n] == 0x3f3f3f3f)  return -1;
    return dist[n];


}


int main()
{
    scanf("%d%d", &n, &m);

    memset(g, 0x3f, sizeof g);

    while ( m -- )
    {
        int a, b, c;
        scanf("%d%d%d", &a, &b, &c);

        g[a][b] = min(g[a][b], c);
    }

    int res = dijkstra();

    printf("%d\n", res);

    return 0;
}