@蓝桥杯国赛 123

题解:

#include<iostream>
#include<vector>
using namespace std;
#define ll long long 
int maxn;
vector<ll>dp,dpsum;
int bitOrd(int n){//二分查找
	int l=0,r=maxn;
	while(l<=r){
		int mid=(l+r)/2;
		if(dp[mid]>=n)r=mid-1;
		else l=mid+1;
	}
	return l;
}
ll nsum(ll l,ll r){//l到r的累加和
	return (r-l+1)*(l+r)/2;
}
ll getRes(ll l,ll r,ll st,ll end){
	if(l==r)return nsum(l,r);
	else{
		ll mid=dpsum[r-1]-dpsum[l];//中间部分的总和
		return nsum(st,l)+mid+nsum(1,end);//左边+中间部分+右边
	}
}
int main(){
	dp.resize(20000000);
	dpsum.resize(20000000);
	dp[0]=0;dpsum[0]=0;
	for(int i=1;1;i++){
		dp[i]=dp[i-1]+i;
		dpsum[i]=dpsum[i-1]+dp[i];
		if(dpsum[i]>=1e12){
			maxn=i;dp.resize(maxn+1);dpsum.resize(maxn+1);
			break;
		}
	}
	int t;cin>>t;
	while(t--){
		ll l,r;cin>>l>>r;
		ll loc1=bitOrd(l),loc2=bitOrd(r),st=l-dp[loc1-1],end=r-dp[loc2-1];
		cout<<getRes(loc1,loc2,st,end);
	}
	return 0;
}