leetcode -- Merge Sorted Array

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.

从后往前遍历，减少移动次数。此题与替换字符串类似

public void merge(int A[], int m, int B[], int n) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int k = m + n - 1;
        int aIdx = m - 1, bIdx = n - 1;
        while(aIdx >= 0 && bIdx >= 0){
            if(A[aIdx] >= B[bIdx]){
                A[k] = A[aIdx];
                aIdx --;
            } else {
                A[k] = B[bIdx];
                bIdx --;
            }
            k --;
        }
        
        while(bIdx >= 0){
            A[k] = B[bIdx];
            bIdx --;
            k --;
        }
    }