Leetcode-practice-log/EASY/0088_Merge_Sorted_Array.py at main · nikhilxagr/Leetcode-practice-log · GitHub

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# 88 - Merge Sorted Array

#Revisit
# Revised
"""
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.
Example 2:

Input: nums1 = [1], m = 1, nums2 = [], n = 0
Output: [1]
Explanation: The arrays we are merging are [1] and [].
The result of the merge is [1].
Example 3:

Input: nums1 = [0], m = 0, nums2 = [1], n = 1
Output: [1]
Explanation: The arrays we are merging are [] and [1].
The result of the merge is [1].
Note that because m = 0, there are no elements in nums1. The 0 is only there to ensure the merge result can fit in nums1.

"""

class Solution(object):
    def merge(self, nums1, m, nums2, n):

        i = m - 1
        j = n - 1
        k = m + n - 1

        while i >= 0 and j >= 0:
            if nums1[i] > nums2[j]:
                nums1[k] = nums1[i]
                i -= 1
            else:
                nums1[k] = nums2[j]
                j -= 1
            k -= 1


        while j >= 0:
            nums1[k] = nums2[j]
            j -= 1
            k -= 1

# Algorithm:

# 1. Initialize three pointers: `i` for the last element of the first array (nums1), `j` for the last element of the second array (nums2), and `k` for the last position of the merged array (nums1).

# 2. Iterate while both `i` and `j` are greater than or equal to 0:
#    - Compare the elements at `nums1[i]` and `nums2[j]`.
#    - If `nums1[i]` is greater, place it at position `k` in `nums1` and decrement `i`.
#    - Otherwise, place `nums2[j]` at position `k` in `nums1` and decrement `j`.
#    - Decrement `k` after each placement.

# 3. If there are remaining elements in `nums2` (i.e., `j` is still greater than or equal to 0), copy them into `nums1` at the appropriate positions.