【网络流】 HDOJ 4289 Control

就是求全图的点割集。。。。先拆点，那么就变成一般的割集了。。。然后求最大流就行了。。。。

#include <iostream>#include <queue>#include <stack>#include <map>#include <set>#include <bitset>#include <cstdio>#include <algorithm>#include <cstring>#include <climits>#include <cstdlib>#include <cmath>#include <time.h>#define maxn 505#define maxm 100005#define eps 1e-7#define mod 1000000007#define INF 0x3f3f3f3f#define PI (acos(-1.0))#define lowbit(x) (x&(-x))#define mp make_pair#define ls o<<1#define rs o<<1 | 1#define lson o<<1, L, mid #define rson o<<1 | 1, mid+1, R#define pii pair<int, int>#pragma comment(linker, "/STACK:16777216")typedef long long LL;typedef unsigned long long ULL;//typedef int LL; using namespace std;LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}// headstruct Edge{int v, c, next;Edge(int v = 0, int c = 0, int next = 0) : v(v), c(c), next(next) {}}E[maxm];queue<int> q;int cntE, H[maxn];int dis[maxn];int cnt[maxn];int cur[maxn];int pre[maxn];int nv, s, t, flow, n, m;void addedges(int u, int v, int c){E[cntE] = Edge(v, c, H[u]);H[u] = cntE++;E[cntE] = Edge(u, 0, H[v]);H[v] = cntE++;}void bfs(){memset(cnt, 0, sizeof cnt);memset(dis, -1, sizeof dis);q.push(t);dis[t] = 0, cnt[0]++;while(!q.empty()) {int u = q.front();q.pop();for(int e = H[u]; ~e; e = E[e].next) {int v = E[e].v;if(dis[v] == -1) {dis[v] = dis[u] + 1;cnt[dis[v]]++;q.push(v);}}}}int isap(){memcpy(cur, H, sizeof H);flow = 0;bfs();int e, f, u = pre[s] = s, minv, pos;while(dis[s] < nv) {if(u == t) {f = INF;for(int i = s; i != t; i = E[cur[i]].v) if(E[cur[i]].c < f) {f = E[cur[i]].c;pos = i;}for(int i = s; i != t; i = E[cur[i]].v) {E[cur[i]].c -= f;E[cur[i] ^ 1].c += f;}flow += f;u = pos;}for(e = H[u]; ~e; e = E[e].next) if(E[e].c && dis[E[e].v] + 1 == dis[u]) break;if(~e) {cur[u] = e;pre[E[e].v] = u;u = E[e].v;}else {if(--cnt[dis[u]] == 0) break;for(e = H[u], minv = nv; ~e; e = E[e].next) if(E[e].c && minv > dis[E[e].v]) {minv = dis[E[e].v];cur[u] = e;}dis[u] = minv + 1;cnt[dis[u]]++;u = pre[u];}}return flow;}void init(){cntE = 0;memset(H, -1, sizeof H);}void work(){int u, v, x, S, T;s = 0, t = 2 * n + 1, nv = t + 1;scanf("%d%d", &S, &T);addedges(s, S, INF);addedges(T + n, t, INF);for(int i = 1; i <= n; i++) {scanf("%d", &x);addedges(i, i + n, x);}for(int i = 1; i <= m; i++) {scanf("%d%d", &u, &v);addedges(u + n, v, INF);addedges(v + n, u, INF);}printf("%d\n", isap());}int main(){while(scanf("%d%d", &n, &m)!=EOF) {init();work();}return 0;}