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• 1.0.24
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• GCD.kt

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fuookami.ospf.kotlin.utils.math.ordinary.GCD.kt Maven / Gradle / Ivy

package fuookami.ospf.kotlin.utils.math.ordinary

import fuookami.ospf.kotlin.utils.math.*
import fuookami.ospf.kotlin.utils.operator.*

internal fun  gcdImpl(x: I, y: I): I where I : Integer, I : Minus {
    val zero = x.constants.zero
    assert(x >= zero)
    assert(y >= zero)

    if (x == zero) {
        return y
    }
    if (y == zero) {
        return x
    }

    var a = x
    var b = y
    while (b != zero) {
        if (a > b) {
            val temp = b
            b = a
            a = temp
        }
        b -= a
    }
    return a
}

internal fun  gcdImpl(numbers: List): I where I : Integer, I : Rem {
    assert(numbers.isNotEmpty())

    val zero = numbers.first().constants.zero
    val restNumbers = numbers.toMutableList()

    while (restNumbers.first() neq restNumbers.last()) {
        for (i in 0 until (restNumbers.size - 1)) {
            if (restNumbers[i] % restNumbers[i + 1] eq zero) {
                restNumbers[i] = restNumbers[i + 1]
            } else {
                restNumbers[i] = restNumbers[i] % restNumbers[i + 1]
            }
        }
        restNumbers.sortDescending()
    }
    return restNumbers.first()
}

fun  gcd(x: I, y: I): I where I : Integer, I : Minus {
    return gcdImpl(x.abs(), y.abs())
}

fun  gcd(numbers: List): I where I : Integer, I : Rem {
    return gcdImpl(numbers.map { it.abs() }.sortedDescending())
}

fun  gcd(x: I, y: I, z: I, vararg numbers: I): I where I : Integer, I : Rem {
    return gcd(listOf(x, y, z) + numbers.toList())
}