88. Merge Sorted Array

Leetcode Array Two Pointers

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]

分析

采用两个指针l1,l2分别指向nums1,nums2的尾部，依次把比较大的元素加入到nums1的后部。

public void merge(int[] nums1, int m, int[] nums2, int n) {
     int l1 = m - 1, l2 = n - 1, k = l1 + l2 + 1;
        while (l1 >= 0 || l2 >= 0) {
            if (l1 >= 0 && l2 >=0) {
                if (nums1[l1] > nums2[l2]) nums1[k--] = nums1[l1--];
                else nums1[k--] = nums2[l2--];
            } else if (l2 >= 0) nums1[k--] = nums2[l2--];
            else break; // do nothing;
        }
}