POJ1459--Power Network(最大流)

#include <stdio.h>
#include <iostream>
#include <string>
#include <algorithm>
#include <math.h>
#include <vector>
#include <queue>
using namespace std;

const int maxn=205*205;
const int INF=999999999;

struct Edge
{
int from,to,cap,flow;
};

int n,m,s,t;
vector<Edge> edges;
vector<int> G[maxn];
bool vis[maxn];
int d[maxn];
int cur[maxn];

void init()
{
for(int i=0;i<maxn;i++)
G[i].clear();
memset(vis,0,sizeof(vis));
memset(d,0,sizeof(d));
memset(cur,0,sizeof(cur));
}

bool BFS()
{
memset(vis,0,sizeof(vis));
queue<int> Q;
Q.push(s);
d[s]=0;
vis[s]=1;
while(!Q.empty())
{
int x=Q.front();
Q.pop();
for(int i=0;i<G[x].size();i++)
{
Edge e=edges[G[x][i]];
if(!vis[e.to] && e.cap>e.flow)
{
vis[e.to]=1;
d[e.to]=d[x]+1;
Q.push(e.to);
}
}
}
return vis[t];
}

int DFS(int x,int a)
{
if(x==t || a==0)
return a;
int flow=0,f;
for(int i=cur[x];i<G[x].size();i++)
{
Edge& e=edges[G[x][i]];
if(d[x]+1 == d[e.to] && (f = DFS(e.to,min(a,e.cap-e.flow)))>0)
{
e.flow+=f;
edges[G[x][i]^1].flow-=f;
flow+=f;
a-=f;
if(a==0)
break;
}
}
return flow;
}

int Maxflow(int s,int t)
{
int flow=0;
while(BFS())
{
memset(cur,0,sizeof(cur));
flow+=DFS(s,INF);
}
return flow;
}

void AddEdge(int from,int to,int cap)
{
struct Edge e;
e.from=from,e.to=to,e.cap=cap,e.flow=0;
edges.push_back(e);
e.from=to,e.to=from,e.cap=0,e.flow=0;
edges.push_back(e);
m=edges.size();
G[from].push_back(m-2);
G[to].push_back(m-1);
}

int main()
{
int np,nc,k;
while(scanf("%d%d%d%d",&n,&np,&nc,&k)!=EOF)
{
int u,v,l;
char ch;
init();
for(int i=0;i<k;i++)
{
cin>>ch>>u>>ch>>v>>ch>>l;
AddEdge(u+1,v+1,l);
}
for(int i=0;i<np;i++)
{
cin>>ch>>v>>ch>>l;
AddEdge(0,v+1,l);
}
for(int i=0;i<nc;i++)
{
cin>>ch>>u>>ch>>l;
AddEdge(u+1,n+1,l);
}
s=0,t=n+1;
int ans=Maxflow(s,t);
printf("%d\n",ans);
}
return 0;
}