[bzoj1532] [POI2005]Kos-Dicing

　　二分答案，比赛与双方选手连边跑最大匹配。。看匹配数是否等于比赛数。

　　dinic大法好++

#include<cstdio>
#include<iostream>
#include<cstring>
using namespace std;
const int maxn=10233,inf=1002333333;
struct zs{
    int too,pre,flow;
}e[maxn<<3];int tot,last[maxn<<1];
int dl[maxn<<1],dis[maxn<<1],cd[maxn];
int i,j,k,n,m,tt,s,t;
 
int ra;char rx;
inline int read(){
    rx=getchar(),ra=0;
    while(rx<'0'||rx>'9')rx=getchar();
    while(rx>='0'&&rx<='9')ra*=10,ra+=rx-48,rx=getchar();return ra;
}
 
inline void insert(int a,int b,int c){
    e[++tot].too=b,e[tot].flow=c,e[tot].pre=last[a],last[a]=tot;
    e[++tot].too=a,e[tot].flow=0,e[tot].pre=last[b],last[b]=tot;
}
bool bfs(){
    int l=0,r=1,now,i;
    memset(dis,255,(t+1)<<2),dl[1]=s,dis[s]=0;
    while(l<r&&dis[t]==-1){
        now=dl[++l];
        for(i=last[now];i;i=e[i].pre)if(e[i].flow&&dis[e[i].too]==-1)
            dis[e[i].too]=dis[now]+1,dl[++r]=e[i].too;
    }
    return dis[t]!=-1;
}
inline int min(int a,int b){return a<b?a:b;}
int dfs(int x,int mx){
    if(x==t)return mx;
    int i,used=0,w;
    for(i=last[x];i;i=e[i].pre)if(e[i].flow&&dis[e[i].too]==dis[x]+1){
        w=dfs(e[i].too,min(e[i].flow,mx-used));if(w){
            e[i].flow-=w,e[i^1].flow+=w,used+=w;
            if(used==mx)return mx;
        }
    }
    dis[x]=-1;return used;
}
inline bool check(int mid){
    register int i;int flow=0;
    for(i=2;i<=tt;i+=2)e[i].flow=1,e[i^1].flow=0;
    for(i=tt+1;i<=tot;i+=2)e[i].flow=mid,e[i^1].flow=0;
    while(bfs())flow+=dfs(s,inf);
    return flow==m;
}
int main(){
    n=read(),m=read();
    s=0,t=n+m+1,tot=1;
    for(i=1;i<=m;i++)
        j=read(),k=read(),insert(j,i+n,1),insert(k,i+n,1),cd[j]++,cd[k]++;
    for(i=1;i<=m;i++)insert(i+n,t,1);tt=tot;
    for(i=1;i<=n;i++)insert(s,i,0);
    int l=(m+n-1)/n,r=0,mid;
    for(i=1;i<=n;i++)if(cd[i]>r)r=cd[i];
    while(l<r){
        mid=l+r>>1;
        if(check(mid))r=mid;else l=mid+1;
    }
    printf("%d
",l);
    return 0;
}