665. Non-decreasing Array

https://leetcode.com/problems/non-decreasing-array/

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 can’t get a non-decreasing array by modify at most one element.

Constraints:

n == nums.length 	
1 <= n <= 10^4 	
-10^5 <= nums[i] <= 10^5

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