树状数组（二维偏序）

题目链接

https://leetcode.cn/problems/maximum-sum-queries/description/

题目大意

题目思路

二维偏序问题 -> 一维排序，一维树状数组！

题目代码

class Solution {
public:
    int sz;
    vector<int> tr;
    int lowbit(int x){return x & -x;}
    void update(int x,int k){
        for(int i = x;i <= sz;i += lowbit(i))
            tr[i] = max(tr[i],k);
    }
    int query(int x){
        int ans = -1;
        for(int i = x;i;i -= lowbit(i)) ans = max(ans,tr[i]);
        return ans;
    }
    vector<int> maximumSumQueries(vector<int>& nums1, vector<int>& nums2, vector<vector<int>>& queries) {
        int n = nums1.size(),m = queries.size();
        vector<array<int,2>> nums(n);
        for(int i = 0;i < n;++i) nums[i] = {nums1[i],nums2[i]};
        vector<array<int,3>> q(m);
        for(int i = 0;i < m;++i) q[i] = {queries[i][0],queries[i][1],i};
       // 离散化
        unordered_set<int> s;
        for(auto x:nums) s.insert(x[1]);
        for(auto x:q)    s.insert(x[1]);
        vector<int> list(s.begin(),s.end());
        sort(list.begin(),list.end());
        sz = list.size();
        map<int,int> mp;
        for(int i = 0;i < sz;++i) mp[list[i]] = i;
       // 一维排序
        sort(nums.begin(),nums.end(),[](const auto& a,const auto& b){return a[0] > b[0];});
        sort(q.begin(),q.end(),[](const auto& a,const auto& b){return a[0] > b[0];});

        tr.resize(sz + 10,-1);

        vector<int> ans(m);
        int idx = 0;
        for(auto qy:q){
            int x = qy[0],y = qy[1],i = qy[2];
            while(idx < n && nums[idx][0] >= x){
                update(sz - mp[nums[idx][1]],nums[idx][0] + nums[idx][1]);
                ++idx;
            }
            ans[i] = query(sz - mp[y]);
        }
        return ans;
    }
};