hdu 3667 Transportation 费用流

#include <stdio.h>
#include <iostream>
#include <string.h>
using namespace std;
const int N=500;
const int MAXE=20000000;
const int inf=1<<30;
int head
,s,t,cnt,n,m,ans,k;
int d
,pre
;
bool vis
;
int q[MAXE];
int flow;
struct Edge
{
int u,v,c,w,next;
}edge[MAXE];

void addedge(int u,int v,int w,int c)
{
edge[cnt].u=u;
edge[cnt].v=v;
edge[cnt].w=w;
edge[cnt].c=c;
edge[cnt].next=head[u];
head[u]=cnt++;
edge[cnt].v=u;
edge[cnt].u=v;
edge[cnt].w=-w;
edge[cnt].c=0;
edge[cnt].next=head[v];
head[v]=cnt++;
}

int SPFA()
{
int l,r;
memset(pre,-1,sizeof(pre));
memset(vis,0,sizeof(vis));
for(int i=0;i<=t;i++) d[i]=inf;
d[s]=0;
l=0;r=0;
q[r++]=s;
vis[s]=1;
while(l<r)
{
int u=q[l++];
vis[u]=0;
for(int j=head[u];j!=-1;j=edge[j].next)
{
int v=edge[j].v;
if(edge[j].c>0&&d[u]+edge[j].w<d[v])
{
d[v]=d[u]+edge[j].w;
pre[v]=j;
if(!vis[v])
{
vis[v]=1;
q[r++]=v;
}
}
}
}
if(d[t]==inf)
return 0;
return 1;
}

void MCMF()
{
flow=0;
while(SPFA())
{
int u=t;
int mini=inf;
while(u!=s)
{
if(edge[pre[u]].c<mini)
mini=edge[pre[u]].c;
u=edge[pre[u]].u;
}
if(flow+mini>=k)
{
ans+=(k-flow)*d[t];
flow=k;
return ;
}
else
{
flow+=mini;
ans+=d[t]*mini;
}
u=t;
while(u!=s)
{
edge[pre[u]].c-=mini;
edge[pre[u]^1].c+=mini;
u=edge[pre[u]].u;
}
}
}

int main()
{
while(scanf("%d%d%d",&n,&m,&k)!=EOF)
{
int i,j;
s=1;t=n;cnt=0;
for(i=0;i<=t+5;i++)
head[i]=-1;
for(i=1;i<=m;i++)
{
int u,v,cost,cap;
scanf("%d%d%d%d",&u,&v,&cost,&cap);
for(j=1;j<=cap;j++)
{
addedge(u,v,cost*(2*j-1),1);
addedge(v,u,-cost*(2*j-1),0);
}
}
ans=0;
MCMF();
if(flow==k)
printf("%d\n",ans);
else printf("-1\n");
}
return 0;
}