結果

問題 No.1300 Sum of Inversions
ユーザー 箱星箱星
提出日時 2020-11-27 22:11:32
言語 Kotlin
(2.1.0)
結果
AC  
実行時間 1,422 ms / 2,000 ms
コード長 4,186 bytes
コンパイル時間 19,702 ms
コンパイル使用メモリ 463,692 KB
実行使用メモリ 126,912 KB
最終ジャッジ日時 2024-07-26 13:06:39
合計ジャッジ時間 61,405 ms
ジャッジサーバーID
（参考情報） 		judge1 / judge5
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 * 34
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.InputStream
import java.io.PrintWriter
import java.util.*

// ModInt
// region
class ModInt(x: Long) {

    companion object {
        //const val MOD = 1000000007L
        const val MOD = 998244353L
    }

    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"
    }

}

val fac = mutableListOf<ModInt>()
val invfac = mutableListOf<ModInt>()

fun fact(n: Long, b: Boolean): ModInt {
    if (fac.count() == 0) {
        fac.add(ModInt(1))
        invfac.add(ModInt(1))
    }
    while (fac.count() <= n) {
        fac.add(fac.last() * ModInt(fac.count().toLong()))
        invfac.add(fac.last().inv())
    }
    return if (b) {
        fac[n.toInt()]
    } else {
        invfac[n.toInt()]
    }
}

fun comb(n: Long, k: Long): ModInt {
    return fact(n, true) * fact(k, false) * fact(n - k, false)
}

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

fun compress(a: Array<Long>): Array<Int> {
    val n = a.count()
    val b = a.sorted().distinct().toTypedArray()
    val c = Array(n) { 0 }
    for (i in 0 until n) {
        c[i] = Arrays.binarySearch(b, a[i])
    }
    return c
}

class BIT(private val n: Int) {
    private val data = LongArray(n) { 0 }

    fun add(i: Int, x: Long) {
        var p = i + 1
        while (p <= n) {
            data[p - 1] += x
            p += p and -p
        }
    }

    fun sum(l: Int, r: Int): Long {
        return sum(r) - sum(l)
    }

    private fun sum(i: Int): Long {
        var r = i
        var s = 0L
        while(r > 0) {
            s += data[r - 1]
            r -= r and -r
        }
        return s
    }
}

fun PrintWriter.solve() = with(FastScanner(System.`in`)) {
    val n = nextInt()
    val a = Array(n) { nextLong() }
    val b = compress(a)
    val bit1 = BIT(n)
    val bit2 = BIT(n)
    val cnt_l = Array(n) { 0L }
    val sum_l = Array(n) { 0L }
    var sum = 0L
    for (i in 0 until n) {
        cnt_l[i] = i - bit1.sum(0, b[i] + 1)
        bit1.add(b[i], 1)
        sum_l[i] = sum - bit2.sum(0, b[i] + 1)
        bit2.add(b[i], a[i])
        sum += a[i]
    }
    val bit3 = BIT(n)
    val bit4 = BIT(n)
    val cnt_r = Array(n) { 0L }
    val sum_r = Array(n) { 0L }
    sum = 0L
    for (i in n - 1 downTo 0) {
        cnt_r[i] = bit3.sum(0, b[i])
        bit3.add(b[i], 1)
        sum_r[i] = bit4.sum(0, b[i])
        bit4.add(b[i], a[i])
        sum += a[i]
    }
    var ans = ModInt(0)
    for (j in 1 until n - 1) {
        ans += ModInt(a[j]) * ModInt(cnt_l[j] * cnt_r[j])
        ans += ModInt(sum_l[j]) * ModInt(cnt_r[j])
        ans += ModInt(sum_r[j]) * ModInt(cnt_l[j])
    }
    println(ans)
}

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

class FastScanner(s: InputStream) {
    private var st = StringTokenizer("")
    private val br = s.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()
}
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