結果

問題 No.1428 PeRmutation Question
コンテスト
ユーザー 箱星
提出日時 2020-12-27 20:29:06
言語 Kotlin
(2.1.0)
結果
AC  
実行時間 630 ms / 2,000 ms
コード長 3,680 bytes
コンパイル時間 14,790 ms
コンパイル使用メモリ 463,568 KB
実行使用メモリ 139,744 KB
最終ジャッジ日時 2024-10-01 19:48:51
合計ジャッジ時間 34,390 ms
ジャッジサーバーID
（参考情報） 		judge5 / judge2
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 30
権限があれば一括ダウンロードができます

ソースコード

diff # 

import java.io.PrintWriter
import java.util.*
import kotlin.math.*

// region ModInt
class ModInt(x: Long) {
    companion object {
        const val MOD = 1000000007L
        //const val MOD = 998244353L
    }

    constructor(y: Int) : this(y.toLong())

    val x = (x % MOD + MOD) % MOD

    operator fun plus(other: ModInt): ModInt {
        return ModInt(x + other.x)
    }

    operator fun minus(other: ModInt): ModInt {
        return ModInt(x - other.x)
    }

    operator fun times(other: ModInt): ModInt {
        return ModInt(x * other.x)
    }

    operator fun div(other: ModInt): ModInt {
        return this * other.inv()
    }

    fun pow(exp: Long): ModInt {
        if (exp == 0L) return ModInt(1L)
        var a = pow(exp shr 1)
        a *= a
        if (exp and 1L == 0L) return a
        return this * a
    }

    fun inv(): ModInt {
        return this.pow(MOD - 2)
    }

    override fun equals(other: Any?): Boolean {
        if (this === other) return true
        if (javaClass != other?.javaClass) return false

        other as ModInt

        if (x != other.x) return false

        return true
    }

    override fun hashCode(): Int {
        return x.hashCode()
    }

    override fun toString(): String {
        return "$x"
    }
}

fun Long.toModInt(): ModInt {
    return ModInt(this)
}

fun Int.toModInt(): ModInt {
    return ModInt(this)
}

const val fac_size = 600000
var fac_initialized = false
val arr_fac = Array(fac_size) { ModInt(1) }
val arr_invfac = Array(fac_size) { ModInt(1) }

fun facInitialize() {
    for (i in 1 until fac_size) {
        arr_fac[i] = arr_fac[i - 1] * ModInt(i)
    }
    arr_invfac[fac_size - 1] = arr_fac[fac_size - 1].inv()
    for (i in fac_size - 2 downTo 1) {
        arr_invfac[i] = arr_invfac[i + 1] * ModInt(i + 1)
    }
    fac_initialized = true
}

fun fac(n: Int): ModInt {
    if (!fac_initialized) facInitialize()
    return arr_fac[n]
}

fun fac(n: Long): ModInt {
    return fac(n.toInt())
}

fun invfac(n: Int): ModInt {
    if (!fac_initialized) facInitialize()
    return arr_invfac[n]
}

fun invfac(n: Long): ModInt {
    return invfac(n.toInt())
}

fun comb(n: Long, k: Long): ModInt {
    return if (k in 0..n) {
        fac(n) * invfac(k) * invfac(n - k)
    } else {
        ModInt(0)
    }
}

fun comb2(n: Long, k: Long): ModInt {
    var numer = ModInt(1)
    var denom = ModInt(1)
    for (i in 0 until k) {
        numer *= ModInt(n - i)
        denom *= ModInt(k - i)
    }
    return numer / denom
}
// endregion

fun PrintWriter.solve() {
    val n = nextInt()
    val p = Array(n) { nextInt() - 1 }
    val map = mutableMapOf<Int, Int>()
    val visited = Array(n) { false }
    for (i in 0 until n) {
        if (!visited[i]) {
            var l = 0
            var v = i
            while (!visited[v]) {
                visited[v] = true
                v = p[v]
                l++
            }
            map[l] = (map[l] ?: 0) + 1
        }
    }
    var half = true
    var ans = fac(n)
    for ((k, v) in map) {
        if (k % 2 == 0 || v >= 2) half = false
        ans /= ModInt(k).pow(v.toLong())
        ans *= invfac(v)
    }
    if (half && n != 1) ans /= ModInt(2)
    println(ans)
}

fun main() {
    val writer = PrintWriter(System.out, false)
    writer.solve()
    writer.flush()
}

// region Scanner
private var st = StringTokenizer("")
private val br = System.`in`.bufferedReader()

fun next(): String {
    while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())
    return st.nextToken()
}

fun nextInt() = next().toInt()
fun nextLong() = next().toLong()
fun nextLine() = br.readLine()!!
fun nextDouble() = next().toDouble()
// endregion
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