# LeetCode: Valid Mountain Array Solution

*Flagging*

## Approach

Make sure the array:

- has one peak only
- does not have any valley
- does not have flat road (2 equal adjacent elements)

## Implementation

1/**2 * @param {number[]} arr3 * @return {boolean}4 */5var validMountainArray = function (arr) {6 let peakCount = 07 let valleyCount = 08 let hasFlatWay = false910 for (let i = 1; i < arr.length - 1; i++) {11 if (arr[i] === arr[i - 1] || arr[i] === arr[i + 1]) {12 hasFlatWay = true13 }14 if (arr[i] > arr[i - 1] && arr[i] > arr[i + 1]) {15 peakCount++16 }17 if (arr[i] < arr[i - 1] && arr[i] < arr[i + 1]) {18 valleyCount++19 }20 }2122 return peakCount === 1 && valleyCount === 0 && !hasFlatWay23}

## Comments

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## Tags

leetcode

array

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