665. Non-decreasing Array

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).

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.

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

題意：判斷給定的序列是否可以最多隻改變一個數字就能得到非遞減序列。
主要難點是分析所有可能的情況，程序必須要知道最小改動的數字位置是什麼地方。
當遇到遞減的情況（A[i]< A[i-1]）時需要進行修改，但是存在兩種情況，1）改動A[i]，2）改動A[i-1]。
如果A[i-2]<=A[i]，則改動A[i]，否則改動A[i-1]，這樣不會影響後面數據的判斷。
代碼如下：

class Solution {
    public boolean checkPossibility(int[] nums) {
        boolean modified=false;
        for(int i=1;i<nums.length;i++){
            if(nums[i]<nums[i-1])
            {
                if(modified)
                    return false;
                if(i<2 || nums[i-2]<=nums[i])
                    nums[i-1]=nums[i];
                else
                    nums[i]=nums[i-1];
                modified=true;
            } 
        }
        return true;
    }
}