[OpenJudge 3063]罪犯问题

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <stack>
#include <vector>
#include <queue>
#include <cstdlib>
using namespace std;

int read() {
	int x = 0, f = 1; char c = getchar();
	while(!isdigit(c)){ if(c == ‘-‘) f = -1; c = getchar(); }
	while(isdigit(c)){ x = x * 10 + c - ‘0‘; c = getchar(); }
	return x * f;
}

#define maxn 200010
#define maxm 801010
#define oo 2147483647

struct Edge { int from, to, flow; } ;
struct Dinic {
	int n, m, s, t, head[maxn], next[maxm];
	Edge es[maxm];
	int vis[maxn], Q[maxn], hd, tl;
	int cur[maxn];
	void init(int _) {
		n = _;
		m = 0; memset(head, -1, sizeof(head));
		return ;
	}
	void AddEdge(int a, int b, int c) {
		es[m] = (Edge){ a, b, c }; next[m] = head[a]; head[a] = m++;
		return ;
	}
	bool BFS() {
		memset(vis, 0, sizeof(vis));
		hd = tl = 0; Q[++tl] = s;
		vis[s] = 1;
		while(hd < tl) {
			int u = Q[++hd];
			for(int i = head[u]; i != -1; i = next[i]) {
				Edge& e = es[i];
				if(!vis[e.to] && e.flow) {
					vis[e.to] = vis[u] + 1;
					Q[++tl] = e.to;
				}
			}
		}
		return vis[t] > 0;
	}
	int DFS(int u, int a) {
		if(u == t || !a) return a;
		int flow = 0, f;
		for(int& i = cur[u]; i != -1; i = next[i]) {
			Edge& e = es[i];
			if(vis[e.to] == vis[u] + 1 && (f = DFS(e.to, min(a, e.flow)))) {
				flow += f; a -= f;
				e.flow -= f; es[i^1].flow += f;
				if(!a) return flow;
			}
		}
		return flow;
	}
	int MinCut(int _, int __) {
		s = _; t = __;
		int flow = 0;
		while(BFS()) {
			for(int i = 1; i <= n; i++) cur[i] = head[i];
			flow += DFS(s, oo);
		}
		return flow;
	}
} sol;

int main() {
	int n = read(), m = read(), k = read();
	
	sol.init(n + 2); int s = n + 1, t = n + 2;
	for(int i = 1; i <= m; i++) {
		int x = read();
		sol.AddEdge(s, x, oo), sol.AddEdge(x, s, 0);
	}
	for(int i = 1; i <= n; i++) {
		int x = abs(read());
		sol.AddEdge(i, x, 1); sol.AddEdge(x, i, 1);
	}
	sol.AddEdge(k, t, oo); sol.AddEdge(t, k, 0);
	
	printf("%d\n", sol.MinCut(s, t));
	
	return 0;
}