Valid Mountain Array Problem & Solution
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
iwith0 < i < arr.length - 1such that:arr[0] < arr[1] < ... < arr[i - 1] < arr[i]arr[i] > arr[i + 1] > ... > arr[arr.length - 1]
See the valid mountain array problem on LeetCode.
C++ Solution
#pragma GCC optimize("Ofast")
#pragma GCC optimization("unroll-loops")
static const int _=[](){std::ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();
class Solution {
public:
bool validMountainArray(vector<int>& arr) {
if (arr.size() < 3) {
return false;
}
int i = 1;
while (i < arr.size() && arr[i - 1] < arr[i]) {
++i;
}
if (i == 1 || i == arr.size()) {
return false;
}
while (i < arr.size() && arr[i - 1] > arr[i]) {
++i;
}
return i == arr.size();
}
};