# [88. Merge Sorted Array (Easy)](https://leetcode.com/problems/merge-sorted-array/)
<p>You are given two integer arrays <code>nums1</code> and <code>nums2</code>, sorted in <strong>non-decreasing order</strong>, and two integers <code>m</code> and <code>n</code>, representing the number of elements in <code>nums1</code> and <code>nums2</code> respectively.</p>
<p><strong>Merge</strong> <code>nums1</code> and <code>nums2</code> into a single array sorted in <strong>non-decreasing order</strong>.</p>
<p>The final sorted array should not be returned by the function, but instead be <em>stored inside the array </em><code>nums1</code>. To accommodate this, <code>nums1</code> has a length of <code>m + n</code>, where the first <code>m</code> elements denote the elements that should be merged, and the last <code>n</code> elements are set to <code>0</code> and should be ignored. <code>nums2</code> has a length of <code>n</code>.</p>
<p> </p>
<p><strong>Example 1:</strong></p>
<pre><strong>Input:</strong> nums1 = [1,2,3,0,0,0], m = 3, nums2 = [2,5,6], n = 3
<strong>Output:</strong> [1,2,2,3,5,6]
<strong>Explanation:</strong> The arrays we are merging are [1,2,3] and [2,5,6].
The result of the merge is [<u>1</u>,<u>2</u>,2,<u>3</u>,5,6] with the underlined elements coming from nums1.
</pre>
<p><strong>Example 2:</strong></p>
<pre><strong>Input:</strong> nums1 = [1], m = 1, nums2 = [], n = 0
<strong>Output:</strong> [1]
<strong>Explanation:</strong> The arrays we are merging are [1] and [].
The result of the merge is [1].
</pre>
<p><strong>Example 3:</strong></p>
<pre><strong>Input:</strong> nums1 = [0], m = 0, nums2 = [1], n = 1
<strong>Output:</strong> [1]
<strong>Explanation:</strong> 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.
</pre>
<p> </p>
<p><strong>Constraints:</strong></p>
<ul>
<li><code>nums1.length == m + n</code></li>
<li><code>nums2.length == n</code></li>
<li><code>0 <= m, n <= 200</code></li>
<li><code>1 <= m + n <= 200</code></li>
<li><code>-10<sup>9</sup> <= nums1[i], nums2[j] <= 10<sup>9</sup></code></li>
</ul>
<p> </p>
<p><strong>Follow up: </strong>Can you come up with an algorithm that runs in <code>O(m + n)</code> time?</p>
**Related Topics**:
[Array](https://leetcode.com/tag/array/), [Two Pointers](https://leetcode.com/tag/two-pointers/), [Sorting](https://leetcode.com/tag/sorting/)
**Similar Questions**:
* [Merge Two Sorted Lists (Easy)](https://leetcode.com/problems/merge-two-sorted-lists/)
* [Squares of a Sorted Array (Easy)](https://leetcode.com/problems/squares-of-a-sorted-array/)
* [Interval List Intersections (Medium)](https://leetcode.com/problems/interval-list-intersections/)
## Solution 1.
```cpp
// OJ: https://leetcode.com/problems/merge-sorted-array/
// Author: github.com/lzl124631x
// Time: O(M + N)
// Space: O(1)
class Solution {
public:
void merge(vector<int>& A, int m, vector<int>& B, int n) {
for (int i = m - 1, j = n - 1, k = m + n - 1; k >= 0; --k) {
if (j < 0 || (i >= 0 && A[i] > B[j])) A[k] = A[i--];
else A[k] = B[j--];
}
}
};
```