LeetCode #88 Merge Sorted Array

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Problem

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

Note

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

Example

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

Output: [1,2,2,3,5,6]

Solution1

Method: Build-in

Time Complexity: O(m + (m + n) log (m + n)) => O((m + n) log (m + n))

Space Complexity:

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class Solution:
    def merge(self, nums1, m, nums2, 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.
        """
        for idx in range(m, m+n):
            nums1[idx] = nums2[idx-m]

        nums1.sort()

Solution2

Method:

Time Complexity: O(m+n)

Space Complexity:

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class Solution:
    def merge(self, nums1, m, nums2, 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.
        """
        idx = m + n - 1
        nums1_idx = m - 1
        nums2_idx = n - 1

        while nums1_idx >= 0 and nums2_idx >= 0:
            if nums2[nums2_idx] >= nums1[nums1_idx]:
                nums1[idx] = nums2[nums2_idx]
                nums2_idx -= 1
            else:
                nums1[idx] = nums1[nums1_idx]
                nums1_idx -= 1
            idx -= 1

        while nums2_idx >= 0:
            nums1[idx] = nums2[nums2_idx]
            nums2_idx -= 1
            idx -= 1