# 941. Valid Mountain Array

題目：<https://leetcode.com/problems/valid-mountain-array/>

解法：直接解，使用一個布林變數 directDown 紀錄是否到達山頂並接著往下走

Python3：

class Solution:
    def validMountainArray(self, arr: list[int]) -> bool:
        if len(arr) < 3:
            return False
        if arr[0] >= arr[1]:
            return False
        directDown = False
        for i in range(1, len(arr) - 1):
            if arr[i + 1] > arr[i]:
                if directDown:
                    return False
            elif arr[i + 1] == arr[i]:
                return False
            else:
                if not directDown:
                    directDown = True
        return directDown

if __name__ == '__main__':
    arr = [0, 3, 2, 1]

    ans = Solution().validMountainArray(arr)

    print(ans)

C：

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

bool validMountainArray(int* arr, int arrSize){
    if (arrSize < 3)
        return false;
    if (arr[0] >= arr[1])
        return false;
    bool directDown = false;
    for (int i = 1; i < arrSize - 1; i++) {
        if (arr[i + 1] > arr[i]) {
            if (directDown)
                return false;
        } else if (arr[i + 1] == arr[i]) {
            return false;
        } else {
            if (!directDown)
                directDown = true;
        }
    }
    return directDown;
}

int main()
{
    int arr[] = {0, 3, 2, 1};
    int arrSize = sizeof(arr) / sizeof(arr[0]);
    
    bool ans = validMountainArray(arr, arrSize);
    
    printf("%s\n", ans ? "True" : "False");
    
    return 0;
}

###### tags: `leetcode` `array`