0088.go

// Source: https://leetcode.com/problems/merge-sorted-array
// Title: Merge Sorted Array
// Difficulty: Easy
// Author: Mu Yang <http://muyang.pro>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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
//   -10^9 <= nums1[i], nums2[j] <= 10^9
//
// Follow up: Can you come up with an algorithm that runs in O(m + n) time?
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package main

// We merge for the largest
func merge(nums1 []int, m int, nums2 []int, n int) {
	i := m - 1
	j := n - 1
	k := m + n - 1

	for i >= 0 && j >= 0 {
		if nums1[i] > nums2[j] {
			nums1[k] = nums1[i]
			i--
			k--
		} else {
			nums1[k] = nums2[j]
			j--
			k--
		}
	}

	for j >= 0 {
		nums1[k] = nums2[j]
		j--
		k--
	}
}