665.非递减数列(Easy)

题解

https://leetcode-cn.com/problems/non-decreasing-array/solution/tan-xin-si-xiang-by-zhang-mo-san/

代码示例

Python 示例

class Solution:
    def checkPossibility(self, nums: List[int]) -> bool:
        errors = 0
        for idx in range(len(nums) - 1):
           if nums[idx] > nums[idx + 1]:
               # 只有当修改不会破坏前一个元素的单调性才允许
               # 不能出现 3 4 2 => 3 2 2 的情况
               if (idx == 0 or nums[idx - 1] <= nums[idx + 1]): 
                   nums[idx] = nums[idx + 1]  # 此处修改会影响 nums[i] 与 nums[i - 1] 的递减关系
               else: # 保底方案
                   nums[idx + 1] = nums[idx] 
               errors += 1
        return bool(errors <= 1)

Go 示例

func checkPossibility(nums []int) bool {
    errors := 0
    n := len(nums)
    for i:= 0; i < n - 1; i++ {
        if errors > 1 { return false }
        if nums[i] > nums[i + 1] {
            if i == 0 || nums[i - 1] <= nums[i + 1] {
                nums[i] = nums[i + 1]
            } else {
                nums[i + 1] = nums[i]
            }
            errors++
        }
    } 
    return errors <= 1
}