nefu500(二分+最大流)

#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;
const int oo=1e9;
const int mm=222222;
const int mn=10005;
int node,src,dest,edge,n,m,x;
int ver[mm],flow[mm],next[mm];
int head[mn],work[mn],dis[mn],q[mn],a[mn];
void prepare(int _node,int _src,int _dest)
{
node=_node,src=_src,dest=_dest;
for(int i=0; i<node; i++)
head[i]=-1;
edge=0;
}
void addedge(int u,int v,int c)
{
ver[edge]=v,flow[edge]=c,next[edge]=head[u],head[u]=edge++;
ver[edge]=u,flow[edge]=0,next[edge]=head[v],head[v]=edge++;
}
bool Dicnic_bfs()
{
int i,u,v,l,r=0;
for(i=0; i<node; ++i)
dis[i]=-1;
dis[q[r++]=src]=0;
for(l=0; l<r; ++l)
for(i=head[u=q[l]]; i>=0; i=next[i])
{
if(flow[i]&&dis[v=ver[i]]<0)
{
dis[q[r++]=v]=dis[u]+1;
if(v==dest)
return 1;
}
}
return 0;
}
int Dicnic_dfs(int u,int exp)
{
if(u==dest)
return exp;
for(int &i=work[u],v,tmp; i>=0; i=next[i])
if(flow[i]&&dis[v=ver[i]]==dis[u]+1&&(tmp=Dicnic_dfs(v,min(exp,flow[i])))>0)
{
flow[i]-=tmp;
flow[i^1]+=tmp;
return tmp;
}
return 0;
}
int Dicnic_flow()
{
int i,ret=0,delta;
while(Dicnic_bfs())
{
for(i=0; i<node; i++)
work[i]=head[i];
while(delta=Dicnic_dfs(src,oo))
ret+=delta;
}
return ret;
}
struct sa
{
int from,to,cost,cap;
}s[mm];

int main()
{
while(scanf("%d%d",&n,&m)!=EOF)
{
memset(s,0,sizeof(s));
memset(a,0,sizeof(a));
int ans=0,maxn=0,sum=0,sumn=0;
bool flag=0;
for(int i=1; i<=n; i++)
{
scanf("%d",&a[i]);
sum+=a[i];
}
for(int i=1; i<=m; i++)
{
scanf("%d%d%d%d",&s[i].from,&s[i].to,&s[i].cost,&s[i].cap);
maxn=max(maxn,s[i].cost);

}
int left=0,right=maxn,mid=-1;
while(left<=right)
{
mid=(left+right)/2;
prepare(n+2,1,n+1);
for(int i=1; i<=m; i++)
{
if(s[i].cost<=mid)
{
addedge(s[i].from,s[i].to,s[i].cap);
}
}
for(int i=1;i<=n;i++)
{
if(a[i]!=0)
addedge(i,n+1,a[i]);
}
sumn=Dicnic_flow();
if(sumn==sum)
{
flag=1;
ans=mid;
right=mid-1;
}
else
{
left=mid+1;
}
}
if(flag==false)
printf("-1\n");
else printf("%d\n",ans);

}
return 0;
}