We use cookies to ensure you have the best browsing experience on our website. Please read our cookie policy for more information about how we use cookies.
  1. Counting Valleys
  2. Discussions

Counting Valleys

  • fabiogunkel
     + 0 comments

    This is a classic stack solution. My answer in Kotlin:

    fun countingValleys(steps: Int, path: String): Int {
    var valleyCount = 0
    var hikeStack : Stack<Char> = Stack()
    path.forEach { stepType ->
        when{
            (hikeStack.isEmpty() || hikeStack.peek() == 'U') && stepType == 'U' -> hikeStack.add('U')
            hikeStack.isEmpty() && stepType == 'D' -> { 
                valleyCount += 1
                hikeStack.add('D') 
            } 
            hikeStack.peek() == 'D' && stepType == 'D' -> hikeStack.add('D')
            else -> hikeStack.pop()
        }
    }
    return valleyCount
}

    The catch is: when we have an empty stack we are in sea level, then if we receive a 'D', we enter a Valley, and will stay inside a valley until the stack is empty again. Same thing for a mountain.