POJ 2481 Cows树状数组

Posted 2021-01-11 zhenghanghu

从8月初就看到了这题，今天猛然想起来，然后把补上了

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<queue>
#include<map>
#include<iomanip> 
#include<algorithm>
#include<vector>
#define INF 2e9
#define maxnode 100000
#define ll long long
#define lowbit(x) (x&(-x))
int dx[4]={0,0,1,-1};
int dy[4]={1,-1,0,0};
using namespace std;

int c[100010];
void update(int index,int dx){
    
    for(;index<=100005;index+=lowbit(index)){
        c[index]+=dx;
    }
}

int getSum(int n){
    int ans=0;
    for(;n>0;n-=lowbit(n)) ans+=c[n];
    return ans;
}

struct node{
    int x,y,id;
    node(int x1=0,int y1=0,int i1=0): x(x1),y(y1),id(i1) {}
    bool operator < (const node &n1)const{
        if( x==n1.x ) return y>n1.y;
        return x<n1.x;
    }
}cow[100005];

int ans[100005];

int main(){
    ios::sync_with_stdio(false);
    
    while(1){
        int n; cin>>n;
        if(n==0) break;
        for(int i=1;i<=n;i++){
            int s,e; cin>>s>>e;
            cow[i]=node(s,e,i);
        }
        sort(cow+1,cow+1+n);
        
        memset(c,0,sizeof(c));
        for(int i=1;i<=n;i++){
            if( (cow[i].x==cow[i-1].x) && (cow[i].y==cow[i-1].y) ) {
                ans[ cow[i].id ] = ans[ cow[i-1].id ];
                update(cow[i].y,1);
            }
            else{
                ans[ cow[i].id ] = getSum(100005)-getSum( cow[i].y-1 );
                update(cow[i].y,1);
            }
        }
        
        for(int i=1;i<=n;i++) cout<<ans[i]<<" "; cout<<endl;
    }
    
    return 0;
}