[leetcode]88. Merge Sorted Array归并有序数组

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]

思路

1.  use pointer i to scan nums1, pointer j to scan nums2

2. find the larger item between such two given arrays

3. throw such item into the new merged array

代码

class Solution {
    public void merge(int[] nums1, int m, int[] nums2, int n) {
        int k = m+n-1; //new merged array's length
        int i = m-1; 
        int j = n-1;
        
        while(j >= 0){
             // kinda merge sort algorithm, find the larger item
            if(i >= 0 && nums1[i] > nums2[j]){
                // throw such item into the new merged array
                nums1[k] = nums1[i];
                i--;
            }else{
                // throw larger item into the new merged array
                nums1[k] = nums2[j];
                j--;
            }
            // make sure from right to left, new merged array is in decescending order
            k--;
        }
    }
}