LeetCode - #88 Merge two sorted arrays

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Difficulty Level: Easy

1. Description

You are given two integer arrays sum in non- decreasing order , and two other integers sum , representing the number of elements in and respectively.nums1nums2mnnums1nums2

Please merge nums2into nums1, so that the merged arrays are also arranged in non- decreasing order .

Note: Ultimately, the merged array should not be returned by the function, but stored in the nums1array . To cope with this situation, nums1the initial length of is m + n, where the mfirst element represents the element that should be merged, and the nlast element is 0, which should be ignored. nums2The length is n.

2. Example

Example 1

输入：nums1 = [1,2,3,0,0,0], m = 3, nums2 = [2,5,6], n = 3
输出：[1,2,2,3,5,6]
解释：需要合并 [1,2,3] 和 [2,5,6] 。
合并结果是 [1,2,2,3,5,6] ，其中斜体加粗标注的为 nums1 中的元素。
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Example 2

输入：nums1 = [1], m = 1, nums2 = [], n = 0
输出：[1]
解释：需要合并 [1] 和 [] 。
合并结果是 [1] 。
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Example 3

输入：nums1 = [0], m = 0, nums2 = [1], n = 1
输出：[1]
解释：需要合并的数组是 [] 和 [1] 。
合并结果是 [1] 。
注意，因为 m = 0 ，所以 nums1 中没有元素。nums1 中仅存的 0 仅仅是为了确保合并结果可以顺利存放到 nums1 中。
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Restrictions:

nums1.length == m + n
nums2.length == n
0 <= m, n <= 200
1 <= m + n <= 200
-10^9 <= nums1[i], nums2[j] <= 10^9

3. Answers

 class MergeSortedArray {
    func merge(_ nums1: inout [Int], _ m: Int, _ nums2: [Int], _ n: Int) {
        var i = m - 1, j = n - 1
        
        while i >= 0 || j >= 0 {
            if j < 0 || (i >= 0 && nums1[i] > nums2[j]) {
                nums1[i + j + 1] = nums1[i]
                i -= 1
            } else {
                nums1[i + j + 1] = nums2[j]
                j -= 1
            }
        }
    }
}
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Main idea: merge from end to end to avoid overwriting.
Time Complexity: O(n)
Space Complexity: O(1)

Repository for the algorithm solution: LeetCode-Swift

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