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941: Valid Mountain Array

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`@@ -30,6 +30,7 @@ My solutions to LeetCode problems in Kotlin.`
`30`	`30`	`\| [773](https://leetcode.com/problems/sliding-puzzle/) \| [Sliding Puzzle](src/main/kotlin/com/schmoczer/leetcode/_0773/SlidingPuzzle.kt) \| Hard \|`
`31`	`31`	`\| [796](https://leetcode.com/problems/rotate-string/) \| [Rotate String](src/main/kotlin/com/schmoczer/leetcode/_0796/RotateString.kt) \| Easy \|`
`32`	`32`	`\| [876](https://leetcode.com/problems/middle-of-the-linked-list/) \| [Middle of the Linked List](src/main/kotlin/com/schmoczer/leetcode/_0876/MiddleOfTheLinkedList.kt) \| Easy \|`
	`33`	`+\| [941](https://leetcode.com/problems/valid-mountain-array/) \| [Valid Mountain Array](src/main/kotlin/com/schmoczer/leetcode/_0941/ValidMountainArray.kt) \| Easy \|`
`33`	`34`	`\| [977](https://leetcode.com/problems/squares-of-a-sorted-array/) \| [Squares of a Sorted Array](src/main/kotlin/com/schmoczer/leetcode/_0977/SquaresOfASortedArray.kt) \| Easy \|`
`34`	`35`	`\| [1089](https://leetcode.com/problems/duplicate-zeros/) \| [Duplicate Zeros](src/main/kotlin/com/schmoczer/leetcode/_1089/DuplicateZeros.kt) \| Easy \|`
`35`	`36`	`\| [1295](https://leetcode.com/problems/find-numbers-with-even-number-of-digits/) \| [Find Numbers with Even Number of Digits](src/main/kotlin/com/schmoczer/leetcode/_1295/FindNumbersWithEvenNumberOfDigits.kt) \| Easy \|`

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	`1`	`+# Valid Mountain Array`
	`2`	`+`
	`3`	+Given an array of integers `arr`, return `true` if and only if it is a valid mountain array.
	`4`	`+`
	`5`	`+Recall that arr is a mountain array if and only if:`
	`6`	`+`
	`7`	+- `arr.length >= 3`
	`8`	+- There exists some `i` with `0 < i < arr.length - 1` such that:
	`9`	+ - `arr[0] < arr[1] < ... < arr[i - 1] < arr[i]`
	`10`	+ - `arr[i] > arr[i + 1] > ... > arr[arr.length - 1]`
	`11`	`+`
	`12`	`+Example 1:`
	`13`	`+`
	`14`	`+> Input: arr = [2,1]`
	`15`	`+>`
	`16`	`+> Output: false`
	`17`	`+`
	`18`	`+Example 2:`
	`19`	`+`
	`20`	`+> Input: arr = [3,5,5]`
	`21`	`+>`
	`22`	`+> Output: false`
	`23`	`+`
	`24`	`+Example 3:`
	`25`	`+`
	`26`	`+> Input: arr = [0,3,2,1]`
	`27`	`+>`
	`28`	`+> Output: true`
	`29`	`+`
	`30`	`+`
	`31`	`+Constraints:`
	`32`	`+`
	`33`	+- `1 <= arr.length <= 10^4`
	`34`	+- `0 <= arr[i] <= 10^4`

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	`1`	`+package com.schmoczer.leetcode._0941`
	`2`	`+`
	`3`	`+class ValidMountainArray {`
	`4`	`+ // Runtime 184ms Beats 89.11%`
	`5`	`+ fun validMountainArray(arr: IntArray): Boolean {`
	`6`	`+ if (arr.size < 3) {`
	`7`	`+ return false`
	`8`	`+ }`
	`9`	`+`
	`10`	`+ var max = -1`
	`11`	`+ var maxInd = 0`
	`12`	`+ // find first local max`
	`13`	`+ for (index in 0 until arr.size) {`
	`14`	`+ val num = arr[index]`
	`15`	`+ if (num > max) {`
	`16`	`+ max = num`
	`17`	`+ maxInd = index`
	`18`	`+ } else {`
	`19`	`+ break`
	`20`	`+ }`
	`21`	`+ }`
	`22`	`+`
	`23`	`+ if (arr[0] == max \|\| arr.last() == max) {`
	`24`	`+ return false`
	`25`	`+ }`
	`26`	`+`
	`27`	`+ // check if all elements after our first max are really descending`
	`28`	`+ for (i in maxInd until arr.lastIndex) {`
	`29`	`+ if (arr[i] <= arr[i + 1]) {`
	`30`	`+ return false`
	`31`	`+ }`
	`32`	`+ }`
	`33`	`+`
	`34`	`+ return true`
	`35`	`+ }`
	`36`	`+}`

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	`1`	`+package com.schmoczer.leetcode._0941`
	`2`	`+`
	`3`	`+import org.junit.jupiter.api.Assertions.assertEquals`
	`4`	`+import org.junit.jupiter.api.BeforeEach`
	`5`	`+import org.junit.jupiter.params.ParameterizedTest`
	`6`	`+import org.junit.jupiter.params.provider.Arguments`
	`7`	`+import org.junit.jupiter.params.provider.MethodSource`
	`8`	`+`
	`9`	`+class ValidMountainArrayTest {`
	`10`	`+ private companion object {`
	`11`	`+ @JvmStatic`
	`12`	`+ fun mountainArrays() = listOf(`
	`13`	`+ Arguments.of(intArrayOf(2, 1), false),`
	`14`	`+ Arguments.of(intArrayOf(3, 5, 5), false),`
	`15`	`+ Arguments.of(intArrayOf(0, 3, 2, 1), true),`
	`16`	`+ )`
	`17`	`+ }`
	`18`	`+`
	`19`	`+ private lateinit var sut: ValidMountainArray`
	`20`	`+`
	`21`	`+ @BeforeEach`
	`22`	`+ fun setUp() {`
	`23`	`+ sut = ValidMountainArray()`
	`24`	`+ }`
	`25`	`+`
	`26`	`+ @ParameterizedTest(name = "{0} is a mountain array: {1}")`
	`27`	`+ @MethodSource("mountainArrays")`
	`28`	+ fun `returns true if it is a valid mountain array`(input: IntArray, expected: Boolean) {
	`29`	`+ val result = sut.validMountainArray(input)`
	`30`	`+`
	`31`	`+ assertEquals(expected, result)`
	`32`	`+ }`
	`33`	`+}`

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