BZOJ 1565 NOI 2009 植物大战僵尸 最小割 拓扑排序

相互保护的植物不可能被吃。即形成环的点全部删去。
剩下的即最大权闭合子图。。。

#include <cstdio>#include <cstring>#include <algorithm>#define FOR(i,j,k) for(i=j;i<=k;++i)using namespace std;const int inf = 0x3f3f3f3f, N = 660, M = 800005;int level[N], cnt = 1, cur[N], v[M], p[M], h[N], q[M], s = 0, t, w[M], a[N], in[N];void add(int a, int b, int c) {    p[++cnt] = h[a]; v[cnt] = b; w[cnt] = c; h[a] = cnt; ++in[a];    p[++cnt] = h[b]; v[cnt] = a; w[cnt] = 0; h[b] = cnt;}bool bfs() {    int f = 0, r = 0, u, i;    for (i = s; i <= t; ++i) if (level[i] != -2) level[i] = -1;    q[r++] = s; level[s] = 1;    while (f < r) {        u = q[f++];        for (i = h[u]; i; i = p[i]) {            if (w[i] && level[v[i]] == -1) {                level[v[i]] = level[u] + 1;                q[r++] = v[i];            }        }    }    return level[t] > 0;}int dfs(int u, int low) {    int i, tmp = 0; int res = 0;    if (u == t) return low;    for (i = cur[u]; i && res < low; i = p[i]) {        if (w[i] && level[v[i]] == level[u] + 1) {            tmp = dfs(v[i], min(w[i], low - res));            w[i] -= tmp; w[i ^ 1] += tmp; res += tmp;            if (w[i]) cur[u] = i;        }    }    if (!res) level[u] = -1;    return res;}int dinic() {    int ans = 0, i;    while (bfs()) {        for (i = s; i <= t; ++i) cur[i] = h[i];        ans += dfs(s, inf);    }    return ans;}int main() {    int i, b, c, d, n, m, ss = 0;    scanf("%d%d", &m, &n);    t = n * m + 1;    FOR(i,1,n*m) {        scanf("%d", &a[i]);        if (a[i] > 0) add(s, i, a[i]);        else add(i, t, -a[i]);        scanf("%d", &b);        while (b--) {            scanf("%d%d", &c, &d);            add(c*n+d+1,i,inf);        }        if (i % n) add(i, i + 1, inf);    }    c = d = 0;    for (i = s; i <= t; ++i) {        if (!in[i]) q[d++] = i;        level[i] = -2;    }    while (c < d) {        b = q[c++]; level[b] = 0;        if (a[b] > 0) ss += a[b];        for (i = h[b]; i; i = p[i]) if (i & 1)            if (!--in[v[i]]) q[d++] = v[i];    }    printf("%d\n", ss - dinic());    return 0;}