88. 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.

# 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.

"""
        Do not return anything, modify nums1 in-place instead.
        """
def merge(nums1, nums2, m, n):
    i, j, k = m - 1, n - 1, 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

nums1 = [1,2,3,0,0,0]
m = 3
nums2 = [2,5,6]
n = 3

merge(nums1, nums2, m, n)
print(nums1)

# op: [1, 2, 2, 3, 5, 6]