# 665. Non-decreasing Array

#### Medium

***

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`).

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**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.
```

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**Constraints:**

* `n == nums.length`
* `1 <= n <= 104`
* `-105 <= nums[i] <= 105`

```python
class Solution:
    def checkPossibility(self, nums: List[int]) -> bool:
        spikes = 0
        for index in range(1, len(nums)):
            if nums[index-1] > nums[index]:
                spikes += 1
                # If this is 2nd index or value at 2-back index is also less than this current index
                if (index-2) < 0 or nums[index-2] <= nums[index]:
                    nums[index-1] = nums[index]
                else:
                    nums[index] = nums[index-1]
        return spikes <= 1
```