【最小割】 HDU 3138 Coconuts

题意 ：两个朋友之间意见不同可以选择断绝关系，或者改变意见

求改变意见的人数+断绝关系数

思路：然后可以想到用最小割

开始为0 连接 源点 

    1 连接 汇点

然后朋友关系 用无向图 连接  

容量各为 一

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <string>
#include <iostream>
#include <algorithm>
#include <sstream>
#include <cmath>
using namespace std;
#include <queue>
#include <stack>
#include <vector>
#include <deque>
#include <map>
#define cler(arr, val)    memset(arr, val, sizeof(arr))
typedef long long  LL;
const int MAXN = 543;
const int MAXM = 260110;
const int INF = 0x3f3f3f3f;
const int mod = 1000000007;
struct Edge
{
    int to,next,cap,flow;
}edge[MAXM];//注意是MAXM
int tol;
int head[MAXN];
int gap[MAXN],dep[MAXN],pre[MAXN],cur[MAXN];
void init()
{
    tol = 0;
    memset(head,-1,sizeof (head));
}
//加边，单向图三个参数，双向图四个参数
void addedge (int u,int v,int w,int rw=0)
{
    edge[tol].to = v;edge[tol].cap = w;edge[tol].next = head[u];
    edge[tol].flow = 0;head[u] = tol++;
    edge[tol].to = u;edge[tol].cap = rw;edge[tol]. next = head[v];
    edge[tol].flow = 0;head[v]=tol++;
}
//输入参数：起点、终点、点的总数
//点的编号没有影响，只要输入点的总数
int sap(int start,int end, int N)
{
    memset(gap,0,sizeof(gap));
    memset(dep,0,sizeof(dep));
    memcpy(cur,head,sizeof(head));
    int u = start;
    pre[u] = -1;
    gap[0] = N;
    int ans = 0;
    int i;
    while(dep[start] < N)
    {
        if(u == end)
        {
            int Min = INF;
            for( i = pre[u];i != -1; i = pre[edge[i^1]. to])
            {
                if(Min > edge[i].cap - edge[i]. flow)
                    Min = edge[i].cap - edge[i].flow;
            }
            for( i = pre[u];i != -1; i = pre[edge[i^1]. to])
            {
                edge[i].flow += Min;
                edge[i^1].flow -= Min;
            }
            u = start;
            ans += Min;
            continue;
        }
        bool flag =  false;
        int v;
        for( i = cur[u]; i != -1;i = edge[i].next)
        {
            v = edge[i]. to;
            if(edge[i].cap - edge[i].flow && dep[v]+1 == dep[u])
            {
                flag =  true;
                cur[u] = pre[v] = i;
                break;
            }
        }
        if(flag)
        {
            u = v;
            continue;
        }
        int Min = N;
        for( i = head[u]; i !=  -1;i = edge[i]. next)
        {
            if(edge[i].cap - edge[i].flow && dep[edge[i].to] < Min)
            {
                Min = dep[edge[i].to];
                cur[u] = i;
            }
        }
        gap[dep[u]]--;
        if(!gap[dep[u]]) return ans;
        dep[u] = Min+1;
        gap[dep[u]]++;
        if(u != start) u = edge[pre[u]^1].to;
    }
    return ans;
}
int n,m,s,e;
void build()
{
    init();
	s=n+1,e=n+2;
	int u,v,w;
	for(int i=1;i<=n;i++)
	{
		scanf("%d",&w);
		if(w==0)
			addedge(s,i,1);
		else
			addedge(i,e,1);

	}
	for(int i=1;i<=m;i++)
	{
		scanf("%d%d",&u,&v);
		addedge(u,v,1);
		addedge(v,u,1);
	}
}
int main()
{
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    // freopen("out.txt", "w", stdout);
#endif
	while(scanf("%d%d",&n,&m),n+m)
	{
	    build();
		printf("%d\n",sap(s,e,n+2));
	}
	return 0;
}