#Leetcode# 373. Find K Pairs with Smallest Sums

https://leetcode.com/problems/find-k-pairs-with-smallest-sums/

You are given two integer arrays nums1 and nums2 sorted in ascending order and an integer k.

Define a pair (u,v) which consists of one element from the first array and one element from the second array.

Find the k pairs (u1,v1),(u2,v2) ...(uk,vk) with the smallest sums.

Example 1:

Input: nums1 = [1,7,11], nums2 = [2,4,6], k = 3
Output: [[1,2],[1,4],[1,6]] 
Explanation: The first 3 pairs are returned from the sequence: 
             [1,2],[1,4],[1,6],[7,2],[7,4],[11,2],[7,6],[11,4],[11,6]

Example 2:

Input: nums1 = [1,1,2], nums2 = [1,2,3], k = 2
Output: [1,1],[1,1]
Explanation: The first 2 pairs are returned from the sequence: 
             [1,1],[1,1],[1,2],[2,1],[1,2],[2,2],[1,3],[1,3],[2,3]

Example 3:

Input: nums1 = [1,2], nums2 = [3], k = 3
Output: [1,3],[2,3]
Explanation: All possible pairs are returned from the sequence: [1,3],[2,3]

代码1：

class Solution {
public:
    vector<pair<int, int>> kSmallestPairs(vector<int>& nums1, vector<int>& nums2, int k) {
        vector<pair<int, int>> res;
        multimap<int, pair<int, int>> m;
        for (int i = 0; i < min((int)nums1.size(), k); ++i) {
            for (int j = 0; j < min((int)nums2.size(), k); ++j) {
                m.insert({nums1[i] + nums2[j], {nums1[i], nums2[j]}});
            }
        }
        for (auto it = m.begin(); it != m.end(); ++it) {
            res.push_back(it->second);
            if (--k <= 0) return res;
        }
        return res;
    }
};

代码2：

class Solution {
public:
    vector<pair<int, int>> kSmallestPairs(vector<int>& nums1, vector<int>& nums2, int k) {
        vector<pair<int, int> > sum;
        vector<pair<int, int> > ans;
        int N = nums1.size(), M = nums2.size();
        
        for(int i = 0; i < min(N, k); i ++) {
            for(int j = 0; j < min(M ,k); j ++) {
                ans.push_back({nums1[i], nums2[j]});
            }
        }
        
        sort(ans.begin(), ans.end(), [](pair<int, int> &a, pair<int, int> &b){return a.first + a.second < b.first + b.second;});
        
        if (ans.size() > k) ans.erase(ans.begin() + k, ans.end());
        return ans;
    }
};

粗门啦！