OrderedSet

Ordered Set

An ordered set is a common data structure that supports O(log N) lookups, insertions and removals. Ordered set is also sometimes used as an alternative to a hash map, for example in STL’s map.

Kotlin playground link

Code

class OrderedSet<T : Comparable<T>>(list: MutableList<T>) {

    var items: MutableList<T> = list

    fun insert(element: T) {
        if (exists(element)) {
            return
        }

        for (i in 0..<this.items.count()) {
            if (this.items[i] > element) {
                this.items.add(i, element)
                return
            }
        }
        this.items.add(element)
    }

    /**
     * Use binarySearch algorithm to find the position for the new element in array
     */

    fun findElementPosition(element: T): Int? {
        var rangeStart = 0
        var rangeEnd = this.items.count()

        while (rangeStart < rangeEnd) {
            val midIndex = rangeStart + (rangeEnd - rangeStart) / 2
            if (this.items[midIndex] == element) {
                return midIndex
            } else if (this.items[midIndex] < element) {
                rangeStart = midIndex + 1
            } else {
                rangeEnd = midIndex
            }
        }
        return null
    }

    override fun toString(): String = this.items.toString()

    fun isEmpty(): Boolean = this.items.isEmpty()

    fun exists(element: T): Boolean = findElementPosition(element) != null

    fun count(): Int = this.items.count()

    fun remove(element: T) {
        val position = findElementPosition(element)
        if (position != null) {
            this.items.removeAt(position)
        }
    }

    fun removeAll() = this.items.removeAll(this.items)

    fun max(): T? {
        return if (count() != 0) {
            this.items[count() - 1]
        } else {
            null
        }
    }

    fun min(): T? {
        return if (count() != 0) {
            this.items[0]
        } else {
            null
        }
    }
}