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Algorithm-88 - 12/4/2023

two pointers in sorted array

You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and nums2 respectively.

Merge nums1 and nums2 into a single array sorted in non-decreasing order.

The final sorted array should not be returned by the function, but instead be stored inside the array nums1. To accommodate this, nums1 has a length of m + n, where the first m elements denote the elements that should be merged, and the last n elements are set to 0 and should be ignored. nums2 has a length of n.

Example 1:

Input: nums1 = [1,2,3,0,0,0], m = 3, nums2 = [2,5,6], n = 3 Output: [1,2,2,3,5,6] Explanation: The arrays we are merging are [1,2,3] and [2,5,6]. The result of the merge is [1,2,2,3,5,6] with the underlined elements coming from nums1.

function merge(nums1: number[], m: number, nums2: number[], n: number): void {
  let i = m - 1;
  let j = n - 1;
  let k = m + n - 1;
  while (i >= 0 && j >= 0) {
    if (nums1[i] >= nums2[j]) {
      nums1[k] = nums1[i];
      i--;
      k--;
    } else {
      nums1[k] = nums2[j];
      j--;
      k--;
    }
  }
  while (j >= 0) {
    nums1[k] = nums2[j];
    k--;
    j--;
  }
}