bzoj1412

bzoj1001 狼抓兔子

bzoj1412 狼抓羊。。。

什麼時候來個狼抓青蛙

狼爪喜羊羊。。。

都是最小割。。。

一個經典的最小割模型

#include <queue>
#include <cstdio>
#include <cstring>
using namespace std;

int n,m;
int a[110][110];

struct edge {
	int v,f,next;
}e[50010];
int cnt = -1,head[10010];

int read_int () {
	char c = getchar();
	int re = 0;
	for(;c > '9' || c < '0';c = getchar());
	for(;c >= '0' && c <= '9';c = getchar())
		re = re * 10 + c - '0';
	return re;
}

int cal (int i,int j) {
	return (i - 1) * m + j;
}

void adde (int u,int v,int f) {
	e[++cnt].v = v;
	e[cnt].f = f;
	e[cnt].next = head[u];
	head[u] = cnt;
	
	e[++cnt].v = u;
	e[cnt].f = f;
	e[cnt].next = head[v];
	head[v] = cnt;
}


int depth[10010];
queue<int>q;
bool bfs () {
	memset(depth,-1,sizeof depth);
	while(!q.empty())
		q.pop();
	depth[0] = 1;
	q.push(0);
	
	while(!q.empty()) {
		int u = q.front();
		q.pop();
		
		for(int i = head[u];i != -1;i = e[i].next) {
			int v = e[i].v;
			if(depth[v] != -1 || !e[i].f)
				continue;
			depth[v] = depth[u] + 1;
			if(v == n * m + 1)
				return 1;
			q.push(v);
		}
	}
	return 0;
}

int dfs (int u,int maxf) {
	if(u == n * m + 1)
		return maxf;
	int leftf = maxf;
	for(int i = head[u];i != -1;i = e[i].next) {
		if(!leftf)
			return maxf;
		
		int v = e[i].v;
		if(depth[v] != depth[u] + 1 || !e[i].f)
			continue;
		
		int t = dfs(v,min(leftf,e[i].f));
		leftf -= t;
		e[i].f -= t;
		e[i ^ 1].f += t;
	}
	depth[u] = -1;
	return maxf - leftf;
}

int main () {
	memset(head,-1,sizeof head);
	n = read_int();
	m = read_int();
	
	for(int i = 1;i <= n;++i)
		for(int j = 1;j <= m;++j)
			a[i][j] = read_int();
	
	for(int i = 1;i <= n;++i)
		for(int j = 1;j <= m;++j) {
			if(a[i][j] == 1)
				adde(0,cal(i,j),0x3f3f3f3f);
			if(a[i][j] == 2)
				adde(cal(i,j),n * m + 1,0x3f3f3f3f);
			if(i + 1 <= n && (a[i + 1][j] != a[i][j] || (a[i + 1][j] == a[i][j] && a[i + 1][j] == 0)))
				adde(cal(i,j),cal(i + 1,j),1);
			if(j + 1 <= m && (a[i][j + 1] != a[i][j] || (a[i][j + 1] == a[i][j] && a[i][j + 1] == 0)))
				adde(cal(i,j),cal(i,j + 1),1);
		}
	
	int ans = 0;
	while(bfs()) {
		ans += dfs(0,0x3f3f3f3f);
	}
	printf("%d\n",ans);
}