HDU 1569 黑白染色+最小割

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;
#define N 3000
#define M 10000
#define inf 1073741824
#define ll int
//N为点数 M为边数

struct Edge{
	int from, to, cap, nex;
}edge[M*10];//注意这个一定要够大 不然会re 还有反向弧

int head[N], edgenum;
void addedge(int u, int v, ll cap){
	Edge E = { u, v, cap, head[u]};
	edge[ edgenum ] = E;
	head[u] = edgenum ++;

	Edge E2= { v, u, 0,   head[v]};
	edge[ edgenum ] = E2;
	head[v] = edgenum ++;
}
int sign[N], s, t;
bool BFS(int from, int to){
	memset(sign, -1, sizeof(sign));
	sign[from] = 0;

	queue<int>q;
	q.push(from);
	while( !q.empty() ){
		int u = q.front(); q.pop();
		for(int i = head[u]; i!=-1; i = edge[i].nex)
		{
			int v = edge[i].to;
			if(sign[v]==-1 && edge[i].cap)
			{
				sign[v] = sign[u] + 1, q.push(v);
				if(sign[to] != -1)return true;
			}
		}
	}
	return false;
}
int Stack[M*4], top, cur[M*4];
ll dinic(){
	ll ans = 0;
	while( BFS(s, t) )
	{
		memcpy(cur, head, sizeof(head));
		int u = s;		top = 0;
		while(1)
		{
			if(u == t)
			{
				ll flow = inf;int loc;//loc 表示 Stack 中 cap 最小的边
				for(int i = 0; i < top; i++)
					if(flow > edge[ Stack[i] ].cap)
					{
						flow = edge[Stack[i]].cap;
						loc = i;
					}

					for(int i = 0; i < top; i++)
					{
						edge[ Stack[i] ].cap -= flow;
						edge[Stack[i]^1].cap += flow;
					}
					ans += flow;
					top = loc;
					u = edge[Stack[top]].from;
			}
			for(int i = cur[u]; i!=-1; cur[u] = i = edge[i].nex)//cur[u] 表示u所在能增广的边的下标
				if(edge[i].cap && (sign[u] + 1 == sign[ edge[i].to ]))break;
			if(cur[u] != -1)
			{
				Stack[top++] = cur[u];
				u = edge[ cur[u] ].to;
			}
			else
			{
				if( top == 0 )break;
				sign[u] = -1;
				u = edge[ Stack[--top] ].from;
			}
		}
	}
	return ans;
}
int n, m;
int idx(int x, int y){return x*m+y;}

int main(){
	int i, j;
	while(~scanf("%d%d",&n,&m)){
		memset(head, -1, sizeof(head)), edgenum = 0;
		s = n*m+1; t = s+1;
		ll sum = 0, now;
		for(i = 1; i <= n; i++)
		{
			for(j = 1; j <= m; j++)
			{
				scanf("%d",&now); sum+=now;
				int num = (i-1)*m+j;
				if((i+j)&1)
				{
					addedge(s, num, now);
					if(i>1) addedge(num, num-m, inf);
					if(i<n)	addedge(num, num+m, inf);
					if(j>1)	addedge(num, num-1, inf);
					if(j<m)	addedge(num, num+1, inf);
				}
				else addedge(num, t, now);
			}
		}
		printf("%d\n", sum-dinic());
	}
	return 0;
}
/*
1 1
10

3 3
75 15 21 
75 15 28 
34 70 5

*/

HDU 1569 黑白染色+最小割

原文：http://blog.csdn.net/acmmmm/article/details/18507225