665.non-decreasing-array.cpp

//  Tag: Array
//  Time: O(N)
//  Space: O(1)
//  Ref: -
//  Note: -

//  Given an array nums with n integers, your task is to check if it could become non-decreasing by modifying at most one element.
//  We define an array is non-decreasing if nums[i] <= nums[i + 1] holds for every i (0-based) such that (0 <= i <= n - 2).
//   
//  Example 1:
//  
//  Input: nums = [4,2,3]
//  Output: true
//  Explanation: You could modify the first 4 to 1 to get a non-decreasing array.
//  
//  Example 2:
//  
//  Input: nums = [4,2,1]
//  Output: false
//  Explanation: You cannot get a non-decreasing array by modifying at most one element.
//  
//   
//  Constraints:
//  
//  n == nums.length
//  1 <= n <= 104
//  -105 <= nums[i] <= 105
//  
//  

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

        return count <= 1;
    }
};