CF589F Gourmet and Banquet（二分答案+最大流）

二分答案，每个时间段一个点，每个菜一个点，连边跑最大流，看是否满流即可。

#include <cstdio>#include <cstring>#include <algorithm>#include <queue>using namespace std;#define ll long long#define inf 0x3f3f3f3f#define N 11000inline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();    return x*f;}int n,h[N],num=1,T=10500,lev[N],tot=0,num1=0,cur[N];struct edge{    int to,next,val;}data[2100000];inline void add(int x,int y,int val){    data[++num].to=y;data[num].next=h[x];h[x]=num;data[num].val=val;    data[++num].to=x;data[num].next=h[y];h[y]=num;data[num].val=0;}inline bool bfs(){    queue<int>q;memset(lev,0,sizeof(lev));    lev[0]=1;q.push(0);    while(!q.empty()){        int x=q.front();q.pop();        for(int i=h[x];i;i=data[i].next){            int y=data[i].to;if(lev[y]||!data[i].val) continue;            lev[y]=lev[x]+1;q.push(y);        }    }return lev[T];}inline int dinic(int x,int low){    if(x==T) return low;int tmp=low;    for(int &i=cur[x];i;i=data[i].next){        int y=data[i].to;if(lev[y]!=lev[x]+1||!data[i].val) continue;        int res=dinic(y,min(tmp,data[i].val));        if(!res) lev[y]=0;else tmp-=res,data[i].val-=res,data[i^1].val+=res;        if(!tmp) return low;    }return low-tmp;}inline bool jud(int x){    num=1;int ans=0;    for(int i=1;i<=n;++i) data[++num].val=x,data[++num].val=0;    while(num<num1) data[++num].val=1,data[++num].val=0;    while(bfs()){memcpy(cur,h,sizeof(cur));ans+=dinic(0,inf);}    return ans==n*x;}int main(){//  freopen("a.in","r",stdin);    n=read();    for(int i=1;i<=n;++i) add(i,T,0);    for(int i=1;i<=n;++i){        int x=read(),y=read();tot=max(tot,y);        for(int j=x+1;j<=y;++j) add(j+n,i,1);    }for(int i=1;i<=tot;++i) add(0,i+n,1);    int l=1,r=tot/n;num1=num;    while(l<=r){        int mid=l+r>>1;        if(jud(mid)) l=mid+1;        else r=mid-1;    }printf("%d\n",(l-1)*n);    return 0;}