Non-decreasing Array

/*
There is three case only:
i)2 4 3 : Down 4 to 3 ie. nums[i-1] to nums[i]
ii)2 4 2 : Down 4 to 2 ie. nums[i-1] to nums[i]
ii)2 4 1 : up 1 to 4 ie. nums[i] to nums[i-1]

One more point,When i<=1 and nums[i]<nums[i-1] then increase nums[i-1] to nums[i] but
we can't access nums[i-2] so just increase the modification count.
when modification count increases than one,return false.
*/

class Solution {
public:
    bool checkPossibility(vector<int>& nums) {
        int modification_count=0;
        for(int i=1;i<nums.size();i++){
            if(i>1 && nums[i]<nums[i-1]){
                modification_count++;
                if(nums[i-2]<=nums[i]) nums[i-1]=nums[i];
                else if(nums[i-2]>nums[i]) nums[i]=nums[i-1];
            }
            else if(i<=1 && nums[i]<nums[i-1]) modification_count++;
            if(modification_count>1) return false;
        }
        return true;
    }
};