/*

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.

*/

// <1> compare sort from the end of array

// <2> copy remaning parts of array B to array A

// time: O(n); space: O(1)

public class Solution {

public void merge(int A[], int m, int B[], int n) {

if (n == 0) return;

int i = m-1, j = n-1;

int index = A.length-1;

while (i >= 0 && j >= 0){

if (A[i] > B[j]) A[index--] = A[i--];

else A[index--] = B[j--];

}

while (j >= 0) A[index--] = B[j--]; // don't forget this step & no need to copy remaing elements in A, understand why

}

}