求助

EK刚学1ms，死循环了。

#include<bits/stdc++.h>

namespace IO {
    inline int read() {
        int ret = 0, f = 1;char ch = getchar();
        while (ch < '0' || ch > '9') {
            if (ch == '-') f = -f;
            ch = getchar();
        }
        while (ch >= '0' && ch <= '9') {
            ret = (ret << 1) + (ret << 3) + (ch ^ 48);
            ch = getchar();
        }
        return ret * f;
    }
    void write(int x) {
        if (x < 0) putchar('-'), x = -x;
        if (x > 9) write(x / 10);
        putchar(x % 10 + '0');
    }
} 

using namespace std;
using namespace IO;

const int maxn = 200 + 5;
const int maxm = 5e3 + 5;

int tot = 1, head[maxn], to[maxm * 2], nxt[maxm * 2], val[maxm * 2];
void add(int u, int v, int c) {
    tot++;
    nxt[tot] = head[u];
    head[u] = tot;
    to[tot] = v;
    val[tot] = c;
}

int n, m, s, t;

struct Node {
    int num, edge;
};

queue<int> q;
int vis[maxm * 2];
Node pre[maxm * 2];
bool bfs() {
    memset(vis, 0, sizeof(vis));
    memset(pre, -1, sizeof(pre));
    q.push(s);
    vis[s] = 1;
    while (!q.empty()) {
        int now = q.front();q.pop();
        for (int i = head[now];i;i = nxt[i]) {
            int v = to[i], Val = val[i];
            if (Val && !vis[v]) {
                pre[v].num = now;
                pre[v].edge = i;
                if (v == t) return 1;
                vis[v] = 1;
                q.push(v);
            }
        }
    }
    return 0;
}

int ans;

void EK() {
    while (bfs()) {
        int minn = INT_MAX;
        for (int i = t;i != s;i = pre[i].num) minn = min(minn, val[pre[i].edge]);
        ans += minn;
        for (int i = t;i != s;i = pre[i].num) {
            val[pre[i].edge] -= minn;
            val[pre[i].edge ^ 1] += minn;
        }
    }
}

int main() {
    n = read(), m = read(), s = read(), t = read();
    for (int i = 1;i <= m;i++) {
        int u = read(), v = read(), c = read();
        add(u, v, c), add(v, u, 0);
    }

    EK();

    printf("%d\n", ans);
    return 0;
}