Algorithms

PercentageRound.kt

// 保证总和为100%的前提下损失精度最小的百分比Rounding算法
import com.google.common.math.IntMath

fun percentageRound(a: List<Double>, precision: Int): List<Double> {
    val factor = IntMath.pow(10, precision)
    val scaled = a.map { it * factor }

    val rounded = scaled.mapIndexed { i, num -> i to Math.round(num) }

    val sum = rounded.fold(0L) { acc, pair -> acc + pair.second }
    var diff = sum - factor

    return if (diff != 0L) {
        val fragment = diff / Math.abs(diff)
        rounded.zip(scaled).sortedBy { (a, b) ->
            (b - a.second) * fragment
        }.map { (a, _) ->
            if (diff != 0L) {
                diff -= fragment
                a.first to a.second - fragment
            } else a.first to a.second
        }
    } else {
        rounded
    }
        .sortedBy { it.first }
        .map { it.second / factor.toDouble() }
}