POJ 2112 Optimal Milking 【网络流】【二分】【最短路】

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<string.h>
#define MAXN 500
#define MAXM 50000
using namespace std;
const int inf=0x3f3f3f3f;
struct Edge
{
    int v,c,f,nx;
    Edge() {}
    Edge(int v,int c,int f,int nx):v(v),c(c),f(f),nx(nx) {}
} E[MAXM];
int G[MAXN],cur[MAXN],pre[MAXN],dis[MAXN],gap[MAXN],sz;
void init()
{
    sz=0; memset(G,-1,sizeof(G));
}
void add_edge(int u,int v,int c)
{
    E[sz]=Edge(v,c,0,G[u]); G[u]=sz++;
    E[sz]=Edge(u,0,0,G[v]); G[v]=sz++;
}
bool bfs(int S,int T)
{
    static int Q[MAXN]; memset(dis,-1,sizeof(dis));
    dis[S]=0; Q[0]=S;
    for (int h=0,t=1,u,v,it;h<t;++h)
    {
        for (u=Q[h],it=G[u];~it;it=E[it].nx)
        {
            if (dis[v=E[it].v]==-1&&E[it].c>E[it].f)
            {
                dis[v]=dis[u]+1; Q[t++]=v;
            }
        }
    }
    return dis[T]!=-1;
}
int dfs(int u,int T,int low)
{
    if (u==T) return low;
    int ret=0,tmp,v;
    for (int &it=cur[u];~it&&ret<low;it=E[it].nx)
    {
        if (dis[v=E[it].v]==dis[u]+1&&E[it].c>E[it].f)
        {
            if (tmp=dfs(v,T,min(low-ret,E[it].c-E[it].f)))
            {
                ret+=tmp; E[it].f+=tmp; E[it^1].f-=tmp;
            }
        }
    }
    if (!ret) dis[u]=-1; return ret;
}
int dinic(int S,int T)
{
    int maxflow=0,tmp;
    while (bfs(S,T))
    {
        memcpy(cur,G,sizeof(G));
        while (tmp=dfs(S,T,inf)) maxflow+=tmp;
    }
    return maxflow;
}
struct e{
    int st,ed,dis;
    e(){}
    e(int a,int b,int c){
        st=a;ed=b;dis=c;
    }
};
bool cmp(e a,e b){
    return a.dis<b.dis;
}
e eee[100050];

int pho[300][300];
int main()
{
    int k,c,m;
    scanf("%d%d%d",&k,&c,&m);
    for(int i=1;i<=k+c;i++){
        for(int j=1;j<=k+c;j++){
            scanf("%d",&pho[i][j]);
            if(pho[i][j]==0&&i!=j){
                pho[i][j]=inf;
            }
        }
    }
    for(int kk=1;kk<=k+c;kk++){
        for(int i=1;i<=k+c;i++){
            for(int j=1;j<=k+c;j++){
                if(pho[i][j]>pho[i][kk]+pho[kk][j]){
                    pho[i][j]=pho[i][kk]+pho[kk][j];
                }
            }
        }
    }
    int num=0;
    for(int i=1;i<=k+c;i++){
        for(int j=1;j<=k+c;j++){
            eee[num++]=e(i,j,pho[i][j]);
        }
    }
    sort(eee,eee+num,cmp);
    int tnum=0;
    int s=0,t=k+c+1;
    int ans=0;
    int l=1,r=50000;
    while(l<=r){
        int mid=(l+r)>>1;
        init();
        for(int j=1;j<=k;j++){
            add_edge(0,j,m);
        }
        for(int j=k+1;j<=k+c;j++){
            add_edge(j,t,1);
        }
        tnum=0;
        while(tnum<num&&eee[tnum].dis<=mid){
            if(eee[tnum].st>k&&eee[tnum].ed<=k){
                add_edge(eee[tnum].ed,eee[tnum].st,1);
            }
            tnum++;
        }
        if(dinic(s,t)>=c)r=mid-1;
        else l=mid+1;
    }
    printf("%d\n",l);
}