https://leetcode.com/problems/merge-sorted-array/description/
class Solution { public: void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) { int i = m - 1, j = n - 1, k = m + n - 1; while (i >= 0 && j >= 0) { if (nums1[i] >= nums2[j]) { nums1[k--] = nums1[i--]; } else { nums1[k--] = nums2[j--]; } } while (j >= 0) { nums1[k--] = nums2[j--]; } } };