URAL 1277 Cops and Thieves 最小割

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#include <bits/stdc++.h>using namespace std;const int maxn = 210;const int maxm = 100010;const int inf = 0x3f3f3f3f;struct G{    int v, cap, next;    G() {}    G(int v, int cap, int next) : v(v), cap(cap), next(next) {}} E[maxm];int p[maxn], T;int d[maxn], temp_p[maxn], qw[maxn]; //d顶点到源点的距离标号,temp_p当前狐优化，qw队列void init(){    memset(p, -1, sizeof(p));    T = 0;}void add(int u, int v, int cap){    E[T] = G(v, cap, p[u]);    p[u] = T++;    E[T] = G(u, 0, p[v]);    p[v] = T++;}bool bfs(int st, int en, int n){    int i, u, v, head, tail;    for(i = 0; i <= n; i++) d[i] = -1;    head = tail = 0;    d[st] = 0;    qw[tail] = st;    while(head <= tail)    {        u = qw[head++];        for(i = p[u]; i + 1; i = E[i].next)        {            v = E[i].v;            if(d[v] == -1 && E[i].cap > 0)            {                d[v] = d[u] + 1;                qw[++tail] = v;            }        }    }    return (d[en] != -1);}int dfs(int u, int en, int f){    if(u == en || f == 0) return f;    int flow = 0, temp;    for(; temp_p[u] + 1; temp_p[u] = E[temp_p[u]].next)    {        G& e = E[temp_p[u]];        if(d[u] + 1 == d[e.v])        {            temp = dfs(e.v, en, min(f, e.cap));            if(temp > 0)            {                e.cap -= temp;                E[temp_p[u] ^ 1].cap += temp;                flow += temp;                f -= temp;                if(f == 0)  break;            }        }    }    return flow;}int dinic(int st, int en, int n){    int i, ans = 0;    while(bfs(st, en, n))    {        for(i = 0; i <= n; i++) temp_p[i] = p[i];        ans += dfs(st, en, inf);    }    return ans;}int main(){    int k, n, m, s, f;    while(~scanf("%d", &k)){        init();        scanf("%d %d %d %d", &n,&m,&s,&f);        for(int i=1; i<=n; i++){            int x;            scanf("%d", &x);            add(i, n+i, x);        }        for(int i=1; i<=m; i++){            int a,b;            scanf("%d %d", &a,&b);            add(a+n, b, inf);            add(b+n, a, inf);        }        int ans = dinic(f+n, s, 2*n+1);        if(ans <= k && s != f) puts("YES");        else puts("NO");    }}
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