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BinarySearch.kt
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BinarySearch.kt
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package binarysearch
fun main() {
val array = intArrayOf(1, 2, 3, 4, 5, 6)
require(binarySearchRecursion(6, array, 0, array.size - 1) == binarySearch(6, array))
require(binarySearchRecursion(4, array, 0, array.size - 1) == binarySearch(4, array))
require(binarySearchRecursion(3, array, 0, array.size - 1) == binarySearch(3, array))
require(binarySearchRecursion(1, array, 0, array.size - 1) == binarySearch(1, array))
require(binarySearchRecursion(0, array, 0, array.size - 1) == binarySearch(0, array))
require(binarySearchRecursion(7, array, 0, array.size - 1) == binarySearch(7, array))
}
fun binarySearchRecursion(key: Int, array: IntArray, min: Int, max: Int): Int {
if (min > max) return -1
val midPoint = (min + max) / 2
return when {
array[midPoint] > key -> binarySearchRecursion(key, array, min, midPoint - 1)
array[midPoint] < key -> binarySearchRecursion(key, array, midPoint + 1, max)
else -> midPoint
}
}
fun binarySearch(key: Int, array: IntArray): Int {
var start = 0
var end = array.size - 1
while (start <= end) {
val midPoint = (start + end) / 2
when {
array[midPoint] > key -> {
end = midPoint - 1
}
array[midPoint] < key -> {
start = midPoint + 1
}
else -> {
return midPoint
}
}
}
return -1
}
/**
* https://leetcode.com/discuss/general-discussion/786126/python-powerful-ultimate-binary-search-template-solved-many-problems
*/
fun binarySearchTemplate(key: Int, array: IntArray): Int {
var left = 0
var right = array.size - 1
while (left < right) {
val mid = left + (right - left) / 2
if (condition(array[mid], key)) {
right = mid
} else {
left = mid + 1
}
}
return left
}
private fun condition(midKey: Int, key: Int): Boolean {
// todo: write this condition logic depend on problems
return midKey >= key
}