941. Valid Mountain Array

Given an array of integers arr, return true if and only if it is a valid mountain array.

Recall that arr is a mountain array if and only if:

• arr.length >= 3

• There exists some i with 0 < i < arr.length - 1 such that:

  • arr[0] < arr[1] < ... < arr[i - 1] < arr[i]
  • arr[i] > arr[i + 1] > ... > arr[arr.length - 1]

class Solution {
public:
    bool validMountainArray(vector<int>& arr) {
        int i = 0;
        for(; i < arr.size() - 1 and arr[i] < arr[i+1]; i++) {}
        if(i == arr.size() - 1) return false; 
        if(i == 0) return false;
        for(; i < arr.size() - 1 and arr[i] > arr[i+1]; i++) {}
        return i == arr.size() - 1;
    }
};