[BZOJ1834]网络扩容 做题笔记

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
const int N=2009,M=5109,inf=0x3fffffff;
int n,m,K;
int head
,e[M<<2],ver[M<<2],c[M<<2],next[M<<2];
int ub[M],vb[M],wb[M],cb[M];
int pre
,pos
,d
;bool vis
;
int s,t,tot=1;

void add (int u,int v,int w,int cost=0) {
ver[++tot]=v;e[tot]=w;c[tot]=cost;next[tot]=head[u];head[u]=tot;
ver[++tot]=u;e[tot]=0;c[tot]=-cost;next[tot]=head[v];head[v]=tot;
}

bool spfa () {
queue<int> q;
memset(vis,0,sizeof(vis));
memset(pre,-1,sizeof(pre));
memset(pos,0,sizeof(pos));
for (int i=0;i<=n+9;i++) d[i]=0x3fffffff; //注意这里，一开始我把n+9错写成了N+9，结果WA了
q.push(s); d[s]=0; vis[s]=1; pre[s]=s;
while (!q.empty()) {
int x=q.front(); q.pop();
for (int i=head[x];i;i=next[i])
if (e[i]&&d[x]+c[i]<d[ver[i]]) {
d[ver[i]]=d[x]+c[i];
pre[ver[i]]=x,pos[ver[i]]=i;
if (!vis[ver[i]]) q.push(ver[i]),vis[ver[i]]=1;
}
vis[x]=0;
}
return pre[t]!=-1;
}

int mcf (bool opt) {
int cost=0,maxflow=0,aug;
while (spfa()) {
aug=0x3fffffff;
for (int i=t;i!=s;i=pre[i])
aug=min(aug,e[pos[i]]);
maxflow+=aug,cost+=aug*d[t];
for (int i=t;i!=s;i=pre[i])
e[pos[i]]-=aug,e[pos[i]^1]+=aug;
}
if (opt) return cost;
return maxflow;
}

int main () {
scanf("%d%d%d",&n,&m,&K);
for (int i=1;i<=m;i++) {
scanf("%d%d%d%d",&ub[i],&vb[i],&wb[i],&cb[i]);
add(ub[i],vb[i],wb[i]);
}
s=1,t=n;
printf("%d ",mcf(0));
s=0,t=n;
add(s,1,K,0);
for (int i=1;i<=m;i++)
add(ub[i],vb[i],inf,cb[i]);
printf("%d\n",mcf(1));
}