Merge Sorted Array Problem


Description

LeetCode Problem 88.

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:

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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: 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:

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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:

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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.

Constraints:

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


Sample C++ Code

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class Solution {
public:
    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
        int i = m + n - 1, j = m - 1;
        int k = 0;
        while (j >= 0) {
            nums1[i] = nums1[j];
            i --;
            j --;
        }
        i ++, j ++;
        while ((j < n) && (i < m + n)) {
            if (nums2[j] < nums1[i]) {
                nums1[k] = nums2[j];
                j ++;
            } else {
                nums1[k] = nums1[i];
                i ++;
            }
            k ++;
        }
        while (j < n) {
            nums1[k] = nums2[j];
            j ++, k ++;
        }
        while (i < m + n) {
            nums1[k] = nums1[i];
            i ++, k ++;
        }
        return;
    }
};




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