链接：

2251. 花期内花的数目

题意

n朵花，有n个花期，m个人在m个时间来，求每个时间有多少朵花

解：

通过差分确定一个时间段内的花数量

再通过离线查询（因为返回答案数组）进行记忆存储，只需要一次遍历

实际代码：

#include<bits/stdc++.h>
using namespace std;
vector<int> fullBloomFlowers(vector<vector<int>>& flowers, vector<int>& people)
{map<int,int>cf;for(const auto& flower:flowers){cf[flower[0]]++;cf[flower[1]+1]--;}vector<int>people_sort=people;sort(people_sort.begin(),people_sort.end());map<int,int>S2S;int num=0;auto it=cf.begin();for(auto p:people_sort){while(it!=cf.end() && it->first<=p){num+=it->second;it++;}S2S[p]=num;}vector<int>ans;for(auto p:people){ans.push_back(S2S[p]);}return ans;
}

限制：

• 1 <= flowers.length <= 5 * 104
• flowers[i].length == 2
• 1 <= starti <= endi <= 109
• 1 <= people.length <= 5 * 104
• 1 <= people[i] <= 109