[Simple Algorithm] 31. Merge two sorted arrays

topic:

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1, making num1 an sorted array.

illustrate:

Initialize nums1 and nums2 with m and n elements, respectively.
You can assume that nums1 has enough space (the space size is greater than or equal to m + n) to hold the elements in nums2.
Example:

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

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

Problem solving ideas:

From the back of the array, take the largest data in order.

 

Code:

class Solution {
public:
    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
      int a=n+m-1, i=m-1, j=n-1;
        while(i>=0 && j>=0)
        {
            if(nums1[i]>=nums2[j])
                nums1[a--]=nums1[i--];
            else
                nums1[a--]=nums2[j--];
        }
        if(j>=0)
        {
            while(j>=0)
            {
                nums1[a--]=nums2[j--];
            }
        }
      
      return;
    }
};