leetcode 665 Non-decreasing Array

题目详情

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).

给定一个整数数组，如果最多改变一个元素的值，就可使整个数组元素的值单调递增。那么我们就返回true，否则返回false。

Example 1:
Input: [4,2,3]
Output: True
Explanation: 把4改成1即可使数组单调递增
Example 2:
Input: [4,2,1]
Output: False
Explanation: 不可能通过改变一个元素使数组单调递增

想法

• 首先设置一个count变量，统计array[i] > array[i+1],如果count大于1就返回false；
• 对于不符合条件的元素，我们要给他重新赋值使整个数组可以满足单调递增

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.