[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]

Explanation

  1. First, getting the correct end index of the merged array, then we can try to compare the end element of both array and putting the bigger one to the end index of the result array.

  2. If one array is finish putting all elements to the result array, then we can simply copy all the elements of another array to the result array.

Solution

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class Solution {
    public void merge(int[] nums1, int m, int[] nums2, int n) {
        int end = m+n-1;
        m -= 1;
        n -= 1;
        while (m >= 0 && n >= 0) {
            nums1[end--] = nums1[m] >= nums2[n] ? nums1[m--] : nums2[n--];
        }
        if (m < 0) {
            while (n >= 0) {
                nums1[end--] = nums2[n--];
            }
        }
    }
}