【模板】spfa

int dis[maxn];
bool vis[maxn];
queue<int>q;

void spfa(int x)
{
    mem(dis, 0x3f);
    mem(vis, false);
    dis[x] = 0;
    q.push(x);
    vis[x] = true;
    while (!q.empty())
    {
        int t = q.front();
        q.pop();
        vis[t] = false;
        for (Re int i = head[t]; i != -1; i = e[i].nxt)
        {
            int u = e[i].u;
            int w = e[i].w;
            if (dis[u] > dis[t] + w)
            {
                dis[u] = dis[t] + w;
                if (!vis[u])
                {
                    q.push(u);
                    vis[u] = true;
                }
            }
        }
    }
}