Given an array A of integers, return true if and only if it is a valid mountain array.
Recall that A is a mountain array if and only if:
A.length >= 3 There exists some i with 0 < i < A.length - 1 such that: A[0] < A[1] < ... A[i-1] < A[i] A[i] > A[i+1] > ... > A[A.length - 1]
Example 1:
Input: [2,1] Output: false Example 2:
Input: [3,5,5] Output: false Example 3:
Input: [0,3,2,1] Output: true
Note:
0 <= A.length <= 10000 0 <= A[i] <= 10000
public class Solution {
public bool ValidMountainArray(int[] A) {
if(A.Length<3){
return false;
}
if(A[0]>A[1]){
return false;
}
bool isIncreasing = true;
for(int i=1;i<A.Length;i++){
if(isIncreasing){
if(A[i-1]>A[i]){
isIncreasing=false;
}
}
else{
if(A[i-1]<=A[i]){
return false;
}
}
}
//check if we found decreasing curve or not
return isIncreasing==false;
}
}Time Complexity: O(n)
Space Complexity: O(1)
