【UVALive】3695 Distant Galaxy（......）

题目

传送门：QWQ

分析

好喵啊~~~~

不会做

正解看蓝书P53吧

代码

#include <cstdio>
#include <algorithm>
using namespace std;
inline int read()
{
    int x = , f = ; char ch = getchar();
    while (ch < '' || ch > ''){if (ch == '-')f = -;ch = getchar();}
    while (ch >= '' && ch <= ''){x = x *  + ch - '';ch = getchar();}
    return x * f;
}
struct Point{
    int x,y;
    bool operator < (const  Point& rhs) const{
        return x<rhs.x;
    }
};
const int maxn=;
Point P[maxn]; int n,m,y[maxn],on[maxn],on2[maxn],left[maxn];
int solve(){
    sort(P,P+n); sort(y,y+n);
    m=unique(y,y+n)-y;
    if(m<=) return n;
    int ans=;
    for(int a=;a<m;a++)
    for(int b=a+;b<m;b++){
        int ymin=y[a], ymax=y[b];
        int k=;
        for(int i=;i<n;i++){
            if(i== || P[i].x!=P[i-].x){
                k++;
                on[k]=on2[k]=;
                left[k]=k==?:left[k-]+on2[k-]-on[k-];
            }
            if(P[i].y>ymin  && P[i].y<ymax) on[k]++;
            if(P[i].y>=ymin && P[i].y<=ymax) on2[k]++;
        }
        if(k<=) return n;
        int M=;
        for(int j=;j<=k;j++){
            ans=max(ans,left[j]+on2[j]+M);
            M=max(M,on[j]-left[j]);
        }
    }
    return ans;
}
int main(){
    int kase=;
    while(scanf("%d",&n)== && n){
        for(int i=;i<n;i++){P[i].x=read();P[i].y=read();y[i]=P[i].y;}
        printf("Case %d: %d\n",++kase,solve());
    }
    return ;
}