bzoj3396 [Usaco2009 Jan]Total flow 水流

#include<bits/stdc++.h>
#define N 100000
#define inf 10000000
using namespace std;
int n,x,y,v;
int first[N+5],nxt[N+5],to[N+5],fl[N+5],siz;
int dis[N+5];
inline char nc()
{
static char buf[100000],*p1=buf,*p2=buf;
return p1==p2&&(p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++;
}
inline int read()
{
int x=0,b=1;
char c=nc();
for(;!(c<='9'&&c>='0');c=nc())if(c=='-')b=-1;
for(;c<='9'&&c>='0';c=nc())x=x*10+c-'0';
return x*b;
}
inline char getc()
{
char c=nc();
for(;!((c<='z'&&c>='a')||(c<='Z'&&c>='A'));)c=nc();
return c;
}
inline bool BFS(int s,int t)
{
queue <int> Q;
for(int i=0;i<=2000;i++)dis[i]=inf;
dis[s]=0,Q.push(s);
while(!Q.empty())
{
int x=Q.front();Q.pop();
for(int i=first[x];i!=-1;i=nxt[i])
{
int u=to[i];
if(fl[i]&&dis[x]+1<dis[u])
{
dis[u]=dis[x]+1;
if(u==t)return true;
Q.push(u);
}
}
}
if(dis[t]==inf)return false;return true;
}
inline int DFS(int s,int f,int t)
{
if(s==t)return f;
int rest=f;
for(int i=first[s];i!=-1;i=nxt[i])
{
int u=to[i];
if(rest&&fl[i]&&dis[u]==dis[s]+1)
{
int tmp=DFS(u,min(rest,fl[i]),t);
if(tmp==0)dis[u]=0;
fl[i]-=tmp;
fl[i^1]+=tmp;
rest-=tmp;
}
}
return f-rest;
}
inline int Dinic(int s,int t)
{
int ans=0;
while(BFS(s,t))
ans+=DFS(s,inf,t);
return ans;
}
inline void add(int x,int y,int z)
{
nxt[siz]=first[x];
first[x]=siz;
to[siz]=y;
fl[siz]=z;
siz++;
}
inline void insert(int x,int y,int z)
{
add(x,y,z),add(y,x,z);
}
int main()
{
freopen("in.txt","r",stdin);
memset(first,-1,sizeof(first));
n=read();
for(int i=1;i<=n;i++)
{
x=getc(),y=getc(),v=read();
insert(x,y,v);
}
printf("%d",Dinic('A','Z'));
return 0;
}