665. Non-decreasing Array

Problem

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 <= 10^4

• -10^5 <= nums[i] <= 10^5

Solution (Java)

class Solution {
    public boolean checkPossibility(int[] nums) {
        int count = 0;
        for (int i = 1; i < nums.length; i++) {
            if (nums[i] < nums[i - 1]) {
                if (i - 2 >= 0 && nums[i] < nums[i - 2]) {
                    nums[i] = nums[i - 1];
                }
                count++;
            }
            if (count >= 2) {
                return false;
            }
        }
        return true;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).