88. Merge Sorted Array

https://leetcode.com/problems/merge-sorted-array/description/

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: 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: 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: 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
-109 <= nums1[i], nums2[j] <= 109
``````
• code
``````class Solution:
def merge(self, nums1: List[int], m: int, nums2: List[int], n: int) -> None:
i = m + n - 1
rear1 = m - 1
rear2 = n - 1
while rear2 >= 0:
if rear1 >= 0 and nums1[rear1] > nums2[rear2]:
nums1[i] = nums1[rear1]
rear1 -= 1
else:
nums1[i] = nums2[rear2]
rear2 -= 1
i -= 1
``````
• code
``````class Solution {
public void merge(int[] nums1, int m, int[] nums2, int n) {
int index1 = m - 1;
int index2 = n - 1;
int endIndex = nums1.length - 1;
while (index2 >= 0){
if(index1 >=0 && nums1[index1] >= nums2[index2]){
nums1[endIndex] = nums1[index1];
index1--;
}else{
nums1[endIndex] = nums2[index2];
index2--;
}
endIndex--;
}
}
}
``````
• code
``````var merge = function(nums1, m, nums2, n) {
let i = m - 1;
let j = n - 1;
let end = m + n - 1;
while (j >= 0){
if (i >= 0 && nums1[i] > nums2[j]) nums1[end--] = nums1[i--]
else nums1[end--] = nums2[j--]
}
};
``````
• code
``````var merge = function(nums1, m, nums2, n) {
for (let i = 0; i < n; nums1[i + m] = nums2[i++]);
nums1.sort((a, b) => a - b);
};
``````