3.17 Leetcode: 2389. Longest Subsequence With Limited Sum 和有限的最长子序列

You are given an integer array nums of length n, and an integer array queries of length m.

Return an array answer of length m where answer[i] is the maximum size of a subsequence that you can take from nums such that the sum of its elements is less than or equal to queries[i].

A subsequence is an array that can be derived from +another array by deleting some or no elements without changing the order of the remaining elements.

思路：（排序 + 前缀和 + upper_bound）

        对nums进行从小到大排序  （因为从小的数开始取  才会最长）然后求前缀和  遍历queries数组  找前缀和中第一个大于q的数的地址（利用upper_bound函数)， 该地址减去 前缀和的初始地址   就是最大长度

相关algorithm库函数用法如下

 代码：

class Solution {
public:
    vector<int> answerQueries(vector<int>& nums, vector<int>& queries) {
        sort(nums.begin(), nums.end());
        vector<int> res;
        int j = 0;
        vector<int> presum(nums.size());
        presum[0] = nums[0];
        for(int i = 1; i < nums.size(); i++) {
            presum[i] = presum[i - 1] + nums[i];
        }
        for(auto q: queries) {
            res.push_back(upper_bound(presum.begin(), presum.end(), q) - presum.begin());
        }
        return res;
    }
};