Merge Sorted Array

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

Note:
You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2. The number of elements initialized in nums1and nums2 are m and n respectively.

Analyse: Comparing these two arrays from back to front. 

Runtime: 4ms

class Solution {
public:
    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
        int index = m + n - 1;
        int index1 = m - 1;
        int index2 = n - 1;
        
        while(index1 >= 0 && index2 >= 0){
            if(nums1[index1] < nums2[index2]) nums1[index--] = nums2[index2--];
            else nums1[index--] = nums1[index1--];
        }
        
        while(index1 >= 0) nums1[index--] = nums1[index1--];
        while(index2 >= 0) nums1[index--] = nums2[index2--];
    }
};