文件目录

#include <bits/stdc++.h>
using namespace std;
int n, m, g[105][105], a, b, c;
int dis[105];
bool vis[105];
void dijk(int s)
{
    memset(dis, 0x3f, sizeof(dis));
    dis[s] = 0;
    while (true)
    {
        int k = 0;
        for (int i = 1; i <= n; i++)
            if (vis[i] == false && dis[k] > dis[i])
                k = i;
        if (k == 0)
            break;
        vis[k] = 1;
        for (int i = 1; i <= n; i++)
            if (i != k && vis[i] == false && g[k][i] != 0 && dis[i] > dis[k] + g[k][i])
                dis[i] = dis[k] + g[k][i];
    }
}
int main()
{
    cin >> n >> m;
    while (m--)
    {
        cin >> a >> b >> c;
        g[a][b] = g[b][a] = c;
    }
    dijk(1);
    int ans = -1;
    for (int i = 1; i <= n; i++)
        ans = max(ans, dis[i]);
    bool f = true;
    for (int i = 1; i <= n; i++)
        if (dis[i] == dis[0])
        {
            f = false;
            break;
        }
    if (f)
        cout << ans;
    else
        cout << -1;
    return 0;
}