valid-mountain-array.go

// 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]
//
//
//
//
//  
// Example 1:
// Input: arr = [2,1]
// Output: false
// Example 2:
// Input: arr = [3,5,5]
// Output: false
// Example 3:
// Input: arr = [0,3,2,1]
// Output: true
//
//  
// Constraints:
//
//
// 	1 <= arr.length <= 104
// 	0 <= arr[i] <= 104
//
//


func validMountainArray(arr []int) bool {
    if len(arr) < 3 {
        return false
    }
    increasing := false
    if arr[0] < arr[1] {
        increasing = true
    } else {
        increasing = false
    }
    breaking := 0
    for i:=1; i<len(arr); i++ {
        if arr[i] == arr[i-1] {
            return false
        }
        if increasing {
            if arr[i] > arr[i-1] {
                continue
            }
            if arr[i] < arr[i-1] {
                breaking = i
                break
            }
        } else {
            if increasing {
                if arr[i] < arr[i-1] {
                    continue
                }
                if arr[i] > arr[i-1] {
                    breaking = i
                    break
                }
            }
        }

    }
    for i:=breaking+1; i<len(arr); i++ {
        if arr[i] == arr[i-1]{
            return false
        }
        if increasing {
            if arr[i] > arr[i-1] {
                return false
            }
        } else {
            if arr[i] < arr[i-1] {
                return false
            }
        }
    }
    return true
}