Leetcode 665. Non-decreasing Array (does not decrement arrays)

Given an array n with integers, your task was to check if it could become non-decreasing by modifying at most 1 ele ment.

We define an array are non-decreasing if array[i] <= array[i + 1] holds for every i (1 <= i < n).

Example 1:

41To get a non-decreasing array.

Example 2:

Input: [4,2,1]output:falseexplanation:you can ' t get a non-decreasing array by modify at the most one element.

Note:the n belongs to [1, 10,000].

Title tag: Array

The topic gives us a nums array, allowing us only one chance to change a number so that the array becomes a non-descending array. Return true if it is possible to do so, return false.

The key to this question is, when meeting a nums[i] > nums[i+1], we are to nums[i] to nums[i+1] or nums[i+1] to nums[i].

If feasible, it is of course the choice to prioritize nums[i] to nums[i+1], which reduces the risk of nums[i+1] > nums[i+2].

Take a look at two things:

A. 1 3 5 4 6 7--1 3 4 4 6 7

When it comes to 5 > 4, it is possible to reduce the 5 to 4 because all the numbers before 4:5 are large.

B. 1 4 5 3 6 7--1 4 5 5 6 7

When encountering 5 > 3, here 3:5 is 4 small, so there is no choice, only 3 liters to 5.

　　

When a second change is required, you can return false directly, without having to complete the remaining array.

Java Solution:

Runtime beats 89.68%

Completion Date: 10/20/2017

Keywords: Array

Key points: Learn about 2 changes and priorities

1 classSolution2 {3      Public BooleanCheckpossibility (int[] nums)4     {5         BooleanModified =false;6         7          for(inti=0; i<nums.length; i++)8         {9             if(I+1 < nums.length && Nums[i] > nums[i+1])Ten             { One                 if(modified)//if modified a number already A                     return false; -                 Else //if it is first time to modify a number -                 { the                     if(I-1 < 0 | | nums[i+1] >= nums[i-1])//if nums[i+1] is larger or equal all numbers before Nums[i] -Nums[i] = nums[i+1];//Change nums[i] as same as nums[i+1] -                     Else //if nums[i+1] isn't larger than all numbers before Nums[i] -NUMS[I+1] = nums[i];//Change nums[i+1] as same as nums[i] +                      -Modified =true; +                 }  A             } at         } -          -         return true; -          -     } -}

Reference: N/A

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Leetcode 665. Non-decreasing Array (does not decrement arrays)