# 88 Merge Sorted Array

## Problem Statement

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`.

Input: nums1 = [1,2,3,0,0,0], m = 3, nums2 = [2,5,6], n = 3
Output: [1,2,2,3,5,6]

## Approach

Three Pointers and assigning values into nums from end. P1 looks at the last entry before the 0 values, P2 at the last entry in nums2 and P3 looks at (m+ n - 1). From there it is a while loop through the array that assigns whatever value at position of the pointers is greater to nums1[p3]. All pointers will be shifted accordingly.
Finally we need another while loop that handles remaining items in nums2.

## Solution

``````var twoSum = function(nums, target) {
let p1 = m - 1; // Pointer for nums1 (excluding trailing zeros)
let p2 = n - 1; // Pointer for nums2
let p3 = m + n - 1; // Pointer for the merged result

while (p1 >= 0 && p2 >= 0) {
if (nums1[p1] > nums2[p2]) {
nums1[p3] = nums1[p1];
p1--;
} else {
nums1[p3] = nums2[p2];
p2--;
}
p3--;
}

// If there are remaining elements in nums2, copy them to nums1
while (p2 >= 0) {
nums1[p3] = nums2[p2];
p2--;
p3--;
}
};
``````

LC

Two Pointers