KotlinLeetCode.kt

// https://leetcode.com/problems/two-sum/submissions/
fun twoSum(nums: IntArray, target: Int): IntArray {
    for (index1 in nums.indices) {
        val startIndex = index1 + 1
        for (index2 in startIndex..nums.lastIndex) {
            if (nums[index1] + nums[index2] == target) {
                return intArrayOf(index1, index2)
            }
        }
    }
    return intArrayOf(0, 1)
}

// https://leetcode.com/problems/container-with-most-water/submissions/
fun maxArea(heights: IntArray): Int {
    var maxArea = 0
    for (index1 in heights.indices) {
        val startIndex = index1 + 1
        for (index2 in startIndex..heights.lastIndex) {
            val tankHeight = Math.min(heights[index1], heights[index2])
            val tankWidth = index2 - index1
            maxArea = Math.max(tankHeight * tankWidth, maxArea)
        }
    }
    return maxArea
}

// https://leetcode.com/problems/count-and-say/submissions/
fun countAndSay(n: Int): String {
    if (n == 1) {
        return "1"
    }

    var answerTillHere = countAndSay(n - 1)
    var currentPosition = 0
    var newString = ""
    while (currentPosition < answerTillHere.length) {
        val cnt = countInstancesOfChar(currentPosition, answerTillHere)
        newString += cnt.toString() + answerTillHere[currentPosition]
        currentPosition += cnt
    }
    return newString
}

fun countInstancesOfChar(startIndex: Int, s: String): Int {
    var count = 0
    for (index in startIndex .. s.lastIndex) {
        if (s[index] == s[startIndex]) {
            count++
        } else {
            return count
        }
    }
    return count
}