leetcode 665 Non-decreasing Array

題目詳情

Given an array with n integers, your task is to check if it could become non-decreasing by modifying at most 1 element.
We define an array is non-decreasing if array[i] <= array[i + 1] holds for every i (1 <= i < n).

給定一個整數數組，若是最多改變一個元素的值，就可以使整個數組元素的值單調遞增。那麼咱們就返回true，不然返回false。

Example 1:
Input: [4,2,3]
Output: True
Explanation: 把4改爲1便可使數組單調遞增
Example 2:
Input: [4,2,1]
Output: False
Explanation: 不可能經過改變一個元素使數組單調遞增

想法

• 首先設置一個count變量，統計array[i] > array[i+1],若是count大於1就返回false；
• 對於不符合條件的元素，咱們要給他從新賦值使整個數組能夠知足單調遞增

解法

Example 1:

Input: [4,2,3]
Output: True
Explanation: You could modify the first 4 to 1 to get a non-decreasing array.

Example 2:

Input: [4,2,1]
Output: False
Explanation: You can't get a non-decreasing array by modify at most one element.