【Leetcode】88. Merge Sorted Array

88. Merge Sorted Array

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.

Note:

• The number of elements initialized in nums1 and nums2 are m and n respectively.
• You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2.

Example:

Input:
nums1 = [1,2,3,0,0,0], m = 3
nums2 = [2,5,6],       n = 3

Output: [1,2,2,3,5,6]

维护三个 index，分别对应数组 A，数组 B，和结果数组。然后 A 和 B 同时从后往前扫，每次迭代中 A 和 B 指向的元素大的便加入结果数组中，然后 index-1，另一个不动。

public void merge(int A[], int m, int B[], int n) {
        if(A==null || B==null)
            return;
        int idx1 = m-1;
        int idx2 = n-1;
        int len = m+n-1;
        while(idx1>=0 && idx2>=0)
        {
            if(A[idx1]>B[idx2])
            {
                A[len--] = A[idx1--];
            }
            else
            {
                A[len--] = B[idx2--];
            }
        }
        while(idx2>=0)
        {
            A[len--] = B[idx2--];
        }        
    }