Marc Lester Tan

I solved this easy LC problem in less than 5 minutes. Solution is very easy and straightforward. I provided two solutions: One that uses the map operator and another using the good ‘ole for loop.

class Solution {
    fun calculateTime(keyboard: String, word: String): Int {
        var prevIndex = 0
        return word.map { w ->
            val index = keyboard.indexOf(w)
            val distance = if(index == prevIndex) 0 else Math.abs(prevIndex - index) 
            prevIndex = index
            distance            
        }.sum()
    }
}

Runtime: 192 ms, faster than 20.00% of Kotlin online submissions for Single-Row Keyboard.
Memory Usage: 35.4 MB, less than 100.00% of Kotlin online submissions for Single-Row Keyboard.

class Solution {
    fun calculateTime(keyboard: String, word: String): Int {
        var prevIndex = 0
        var sum = 0
        for(w in word){
            val index = keyboard.indexOf(w)
            val distance = if(index == prevIndex) 0 else Math.abs(prevIndex - index) 
            prevIndex = index
            sum += distance
        }
        
        return sum
    }
}

Runtime: 168 ms, faster than 80.00% of Kotlin online submissions for Single-Row Keyboard.
Memory Usage: 35.5 MB, less than 100.00% of Kotlin online submissions for Single-Row Keyboard.

Why is map operator slower than for-loop? I also seems to notice that this is always the case. Would any have a good explanation about this?