LeetCode Problem - Link


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.



Sequential Approach

In the first step, I got rid of the zeroes at indexes at m and greater than m. Anything in these, I replaced them the secondary array one by one to the end of the array length

Finally sorting, and done.


Gotchas: Trying to solve this via JavaScript `sort`, and `slice` didn't work. I think it's the way LeetCode's internal variables work, you cannot assign a new array, and you'll have to directly manipulate it.


/**
 * @param {number[]} nums1
 * @param {number} m
 * @param {number[]} nums2
 * @param {number} n
 * @return {void} Do not return anything, modify nums1 in-place instead.
 */
var merge = function (nums1, m, nums2, n) {
    // nums1 = [1,2,3,0,0,0]
    // nums2 = [2,5,6]
    for (var i = 0; i < nums1.length; i++) {
        if (i >= m) {
            nums1[i] = nums2[i - m]
        }
    }


    // now sort
    // selection sort, not the fastest, but works
    for (var i = 0; i < nums1.length; i++) {
        for (var j = i + 1; j < nums1.length; j++) {
            if (nums1[i] > nums1[j]) {
                var temp = nums1[i]
                nums1[i] = nums1[j]
                nums1[j] = temp
            }
        }
    }
}