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].
class Solution {
public boolean checkPossibility(int[] a) {
int modified = 0;
for (int i = 1; i < a.length; i++) {
if (a[i] < a[i - 1]) {
if (modified++ > 0) return false;
if (i - 2 < 0 || a[i - 2] <= a[i]) a[i - 1] = a[i]; // lower a[i - 1]
else a[i] = a[i - 1]; // rise a[i]
}
}
return true;
}
}
We can also do it without modifying the input by using a variable prev to hold the a[i-1]; if we have to lower a[i] to match a[i-1] instead of raising a[i-1], simply skip updating prev;
without modified
class Solution {
public boolean checkPossibility(int[] a) {
int modified = 0;
for (int i = 1, prev = a[0]; i < a.length; i++) {
if (a[i] < prev) {
if (modified++ > 0) return false;
if (i - 2 >= 0 && a[i - 2] > a[i]) continue;
}
prev = a[i];
}
return true;
}
}
原文：http://www.cnblogs.com/apanda009/p/7659316.html