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--;
}
};