0088.Merge_Sorted_Array.py

/*
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.
*/

//version:python

class Solution:
    def merge(self, nums1: List[int], m: int, nums2: List[int], n: int) -> None:
        """
        Do not return anything, modify nums1 in-place instead.
        """
        index = len(nums1) - 1
        m -= 1
        n -= 1
        
        while m >= 0 and n >= 0:
            if nums1[m] > nums2[n]:
                nums1[index] = nums1[m]
                m -= 1
                index -= 1

            else:
                nums1[index] = nums2[n]
                n -= 1
                index -= 1
        
        while m >= 0:
            nums1[index] = nums1[m]
            m -= 1
            index -= 1
            
        while n >= 0:
            nums1[index] = nums2[n]
            n -= 1
            index -= 1


class Solution {
    public void merge(int[] nums1, int m, int[] nums2, int n) {
        int index = nums1.length - 1;
        int i = m -1, j = n - 1;
        while ((i >= 0) && (j >= 0)) {
            if (nums2[j] >= nums1[i]) {
                nums1[index--] = nums2[j--];
            } else {
                nums1[index--] = nums1[i--];
            }
        }    
        
        while (i >= 0) {
            nums1[index--] = nums1[i--];
        }
        while (j >= 0) {
            nums1[index--] = nums2[j--];
        }
    }
}