nowcoder contest/911/F

https://ac.nowcoder.com/acm/contest/911/F

 值域上维护右括号的个数，遇到左括号就查询前面有几个右括号

#include <iostream>
#include <algorithm>
#include <queue>
using namespace std ;
 const int N =1e5+10;
 int n,c[N];
 int L[N],R[N] ;
 int lowbit(int x){
 	return x&-x;
 }
 int qry(int x){
 	int res=0;
 	for(;x;x-=lowbit(x)) res+=c[x];
 	return res;
 }
 void add(int x){
 	for(;x<=1e5;x+=lowbit(x)) c[x]++;
 }
 
 signed main(){
 	cin>>n;
 	for(int i=1;i<=n;i++){
 		double x,r; cin>>x>>r;
 		L[i] =x-r; R[i]=x+r;
 	}
 	sort(L+1,L+1+n);sort(R+1,R+1+n) ;
 	
 	int ans=0;
 	for(int i=1;i<=n;i++){
 		int l=L[i],r=R[i];
 		ans+= qry(L[i]-1);
 		add(R[i]);
 	}
 	cout<<ans;
 }