【BZOJ2039】[2009国家集训队]employ人员雇佣【最小割】

【题目链接】

【POPOQQQ的题解】

被卡题意了。。

/* Think Thank Thunk */
#include 
#include 
#include 

using namespace std;

typedef long long LL;

const int maxn = 1005, maxm = 5000005, maxq = maxn;
const LL linf = 0x3f3f3f3f3f3f3f3fLL;

int n, cur[maxn], head[maxn], cnt, bg, ed, depth[maxn], q[maxq];
LL A[maxn];

struct _edge {
	int v; LL w; int next;
} g[maxm << 1];

inline int iread() {
	int f = 1, x = 0; char ch = getchar();
	for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1;
	for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';
	return f * x;
}

inline void add(int u, int v, LL w) {
	g[cnt] = (_edge){v, w, head[u]};
	head[u] = cnt++;
}

inline void insert(int u, int v, LL w) {
	add(u, v, w); add(v, u, 0);
}

inline bool bfs() {
	for(int i = 0; i <= ed; i++) depth[i] = -1;
	int h = 0, t = 0, u, i; depth[q[t++] = bg] = 0;
	while(h != t) for(i = head[u = q[h++]]; ~i; i = g[i].next) if(g[i].w && !~depth[g[i].v]) {
		depth[g[i].v] = depth[u] + 1;
		if(g[i].v == ed) return 1;
		q[t++] = g[i].v;
	}
	return 0;
}

inline LL dfs(int x, LL flow) {
	if(x == ed) return flow;
	LL left = flow;
	for(int i = cur[x]; ~i; i = g[i].next) if(g[i].w && depth[g[i].v] == depth[x] + 1) {
		LL tmp = dfs(g[i].v, min(left, g[i].w));
		left -= tmp; g[i].w -= tmp; g[i ^ 1].w += tmp;
		if(g[i].w) cur[x] = i;
		if(!left) return flow;
	}
	if(left == flow) depth[x] = -1;
	return flow - left;
}

int main() {
	n = iread(); bg = 0; ed = n + 1;
	for(int i = 0; i <= ed; i++) head[i] = -1; cnt = 0;

	for(int i = 1; i <= n; i++) {
		int x = iread();
		insert(i, ed, x);
	}

	LL ans = 0;
	for(int i = 1; i <= n; i++) for(int j = 1; j <= n; j++) {
		int x = iread(); ans += x;
		if(i >= j) continue;
		A[i] += x; A[j] += x;
		insert(i, j, (LL)x << 1);
		insert(j, i, (LL)x << 1);
	}
	for(int i = 1; i <= n; i++) insert(bg, i, A[i]);

	while(bfs()) {
		for(int i = 0; i <= ed; i++) cur[i] = head[i];
		ans -= dfs(bg, linf);
	}

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