Merge Sorted Array

88. Merge Sorted Array

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.

Note: You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2. The number of elements initialized in nums1 and nums2 are m and n respectively.

S: read-write pointer, backward.

从前往后写会覆盖nums1的元素，所以考虑从后往前

void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
  for(int idx = m+n-1, idx1 = m-1, idx2 = n-1; idx >= 0; --idx){
      if(idx1 < 0)  nums1[idx] = nums2[idx2--];
      else if(idx2 < 0) nums1[idx] = nums1[idx1--];
      else nums1[idx] = nums1[idx1] >= nums2[idx2]? nums1[idx1--]: nums2[idx2--]; 
  }
}