88. Merge Sorted Array

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

 Notice

You may assume that A has enough space (size that is greater or equal to m + n) to hold additional elements from B. The number of elements initialized in A and B are m and n respectively.

Example

A = [1, 2, 3, empty, empty], B = [4, 5]

After merge, A will be filled as [1, 2, 3, 4, 5]

分析：

这题的确很简单，用两个pointer分别指向两个array的最后一个数，然后根据它们的大小依次把它们添加到array A里（从末到头添加）

public class Solution {
    public void merge(int[] A, int m, int[] B, int n) {
        int pa = m - 1, pb = n - 1, p = m + n - 1;
        
        while (pa >= 0 || pb >= 0) {
            int a = pa >= 0 ? A[pa] : Integer.MIN_VALUE;
            int b = pb >= 0 ? B[pb] : Integer.MIN_VALUE;
            if (a >= b) {
               A[p] = a;
                pa--;
            } else {
                A[p] = b;
                pb--;
            }
            p--;
        }
    }
}