💡 LeetCode 88 - Merge Sorted

문제

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.

입출력 예제

✅ 예제 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.

✅ 예제 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].

✅ 예제 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.

제약조건

• nums1.length == m + n
• nums2.length == n
• 0 <= m, n <= 200
• 1 <= m + n <= 200
• -109 <= nums1[i], nums2[j] <= 109

작성 코드

class Solution {
	public void merge(int[] nums1, int m, int[] nums2, int n) {
		// 1. 변수 선언 및 초기화
		int index1 = m - 1;
		int index2 = n - 1;
		int indexResult = m + n - 1;
		int value1 = 0; int value2 = 0;
		
		// 2. 순회하며 배열 역순으로 초기화
		while (indexResult >= 0) {
			if (index1 < 0) {
				nums1[indexResult--] = nums2[index2--];
			} else if (index2 < 0) {
				nums1[indexResult--] = nums1[index1--]; 
			} else {
				value1 = nums1[index1];
				value2 = nums2[index2];
				if (value1 >= value2) {
					nums1[indexResult--] = value1;
					index1--;
				} else {
					nums1[indexResult--] = value2;
					index2--;
				}
			}
		}
	}
}

• 역순으로 배열을 초기화하지 않는다면 배열 원소를 옮기는 과정도 추가된다.