POJ 2391 —— Ombrophobic Bovines 二分+Floyd+最大流

原题：http://poj.org/problem?id=2391

#include
#include
#include
#include
#include
#define inf 1LL<<60
#define ll long long
using namespace std;
const int maxn = 500;
const int maxm = 50000;
int f, p;
int num_nodes;
ll dis[maxn][maxn];
int a[maxn][2];

struct Edge  
{  
    int from, to;
	ll flow, cap;  
}edge[maxm*2];  
  
vectorG[maxn]; 
int edgenum;  
void add(int u, int v, ll c)
{  
    edge[edgenum].from = u;  
    edge[edgenum].to = v;  
    edge[edgenum].flow = 0;  
    edge[edgenum].cap = c;  
    edgenum++;  
      
    edge[edgenum].from = v;  
    edge[edgenum].to = u;  
    edge[edgenum].flow = 0;  
    edge[edgenum].cap = 0;  
    edgenum++;  
      
    G[u].push_back(edgenum-2);  
    G[v].push_back(edgenum-1);  
}  
  
int deep[maxn];  
bool vis[maxn];  
void BFS(int s, int t)  
{  
    queueQ;  
    memset(vis, false, sizeof vis);  
    Q.push(t);  
    vis[t] = true;  
    deep[t] = 0;  
    while(!Q.empty())  
    {  
        int now = Q.front();  
        Q.pop();  
        for(int i = 0;i<(int)G[now].size();i++)  
        {  
           	int v = edge[G[now][i]].to;  
            if(!vis[v]) 
			{  
                deep[v] = deep[now] + 1;  
                vis[v] = true;  
                Q.push(v);  
            }  
        }  
    }  
}  
  
int gap[maxn]; 
int cur[maxn]; 
int front[maxn]; 
int Augment(int s, int t)  
{  
    ll minflow = inf;  
    int begin = t;  
    while(begin != s)  
    {  
        Edge& e = edge[front[begin]];  
        minflow = min(minflow, e.cap - e.flow);  
        begin = e.from;  
    }  
      
    begin = t;  
    while(begin != s)  
    {  
        edge[front[begin]].flow += minflow;  
        edge[front[begin]^1].flow -= minflow;  
        begin = edge[front[begin]].from;  
    }  
    return minflow;  
}  
  
ll Maxflow(int s, int t)  
{  
    ll flow = 0;  
    BFS(s, t);  
    memset(gap, 0, sizeof gap);  
    memset(cur, 0, sizeof cur);  
    for(int i = 0;i e.flow && deep[begin] == deep[e.to] + 1) 
			{  
                front[e.to] = G[begin][i];  
                cur[begin] = i;  
                flag = true;  
                begin = e.to;  
                break;  
            }  
        }  
        
        if(!flag) 
        {  
            int k = num_nodes-1;  
            for(ll i = 0;i<(int)G[begin].size();i++) 
			{  
                Edge& e = edge[G[begin][i]];  
                if(e.cap > e.flow)  
                    k = min(k, deep[e.to]);  
            }  
            if(--gap[deep[begin]] == 0) break;  
            gap[deep[begin] = k+1]++;  
            cur[begin] = 0;  
            if(begin != s)   
                begin = edge[front[begin]].from;   
        }  
    }  
    return flow;  
}  
  
void init() 
{  
    for(int i = 0;i