088. Merge Sorted Array.py

# Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.

# Note:
# You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2. The number of elements initialized in nums1 and nums2 are m and n respectively.

# Thinking that from back to front which give chance to modify least
# situation one nums1 exist just return
# situation two nums2 exist just put each num in nums2 into nums1 for that position
class Solution(object):
    def merge(self, nums1, m, nums2, n):
        """
        O(n)
        :type nums1: List[int]
        :type m: int
        :type nums2: List[int]
        :type n: int
        :rtype: void Do not return anything, modify nums1 in-place instead.
        """
        i = m -1 
        j = n -1
        k = m + n - 1
        # at lease one finish
        while i>=0 and j>=0:
            if nums1[i] > nums2[j]:
                nums1[k] = nums1[i]
                i -= 1
                k -= 1
            else:
                nums1[k] = nums2[j]
                j -= 1
                k -= 1
        while j>=0:
            nums1[k] = nums2[j]
            j -= 1
            k -= 1