LeetCode – Merge Sorted Array (Java)_java given two sorted integer arrays a and b, merg-优快云博客

本文介绍了一种将两个已排序的整数数组合并为一个有序数组的方法，并提供了两种Java实现方案。通过从数组末尾开始比较并移动元素的方式，确保合并后的数组依然保持有序状态。

Problem:

Given two sorted integer arrays A and B, merge B into A as one sorted array.

Note:
You may assume that A has enough space to hold additional elements from B. The number of elements initialized in A and B are m and n respectively.

Thoughts for This Problem

The key to solve this problem is moving element of A and B backwards. If B has some elements left after A is done, also need to handle that case.

The takeaway message from this problem is that the loop condition. This kind of condition is also used formerging two sorted linked list.

Java Solution 1

public class Solution {
    public void merge(int A[], int m, int B[], int n) {
 
        while(m > 0 && n > 0){
            if(A[m-1] > B[n-1]){
                A[m+n-1] = A[m-1];
                m--;
            }else{
                A[m+n-1] = B[n-1];
                n--;
            }
        }
 
        while(n > 0){
            A[m+n-1] = B[n-1];
            n--;
        }
    }
}

Java Solution 2

The loop condition also can use m+n like the following.

public void merge(int A[], int m, int B[], int n) {
	int i = m - 1;
	int j = n - 1;
	int k = m + n - 1;
 
	while (k >= 0) {
		if (j < 0 || (i >= 0 && A[i] > B[j]))
			A[k--] = A[i--];
		else
			A[k--] = B[j--];
	}
}