941. Valid Mountain Array --------E

Q:

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:

1. 0 <= A.length <= 10000
2. 0 <= A[i] <= 10000 

A:

class Solution {
public:
    bool validMountainArray(vector<int>& A) {
        int n = A.size();
        if(n<3)
            return false;
        int peak = -1;
        for(int i =0;i<n-1;i++){
            if(A[i] >= A[i+1]){
                peak = i;
                break;
            }
        }
        if(peak<=0)
            return false;
        
        for(int i = peak;i<n-1;i++){
            if(A[i] <= A[i+1])
                return false;
        }
        
        return true;
    }
};