Formatted question description: https://leetcode.ca/all/896.html
896. Monotonic Array (Easy)
An array is monotonic if it is either monotone increasing or monotone decreasing.
An array A is monotone increasing if for all i <= j, A[i] <= A[j]. An array A is monotone decreasing if for all i <= j, A[i] >= A[j].
Return true if and only if the given array A is monotonic.
Example 1:
Input: [1,2,2,3] Output: true
Example 2:
Input: [6,5,4,4] Output: true
Example 3:
Input: [1,3,2] Output: false
Example 4:
Input: [1,2,4,5] Output: true
Example 5:
Input: [1,1,1] Output: true
Note:
1 <= A.length <= 50000-100000 <= A[i] <= 100000
Companies:
Facebook
Related Topics:
Array
Solution 1.
// OJ: https://leetcode.com/problems/monotonic-array/
// Time: O(N)
// Space: O(1)
class Solution {
public:
bool isMonotonic(vector<int>& A) {
int dir = 0;
for (int i = 1; i < A.size(); ++i) {
int d = A[i] == A[i - 1] ? 0 : (A[i] > A[i - 1] ? 1 : -1);
if (dir && d && dir != d) return false;
if (d) dir = d;
}
return true;
}
};
Java
class Solution {
public boolean isMonotonic(int[] A) {
int length = A.length;
if (length <= 2)
return true;
int prevDifference = 0;
for (int i = 1; i < length; i++) {
int difference = A[i] - A[i - 1];
if (prevDifference > 0 && difference < 0 || prevDifference < 0 && difference > 0)
return false;
if (difference != 0)
prevDifference = difference;
}
return true;
}
}