結果

問題 No.1124 Earthquake Safety
コンテスト
ユーザー yakamoto
提出日時 2020-07-22 23:17:22
言語 Kotlin
(2.1.0)
結果
AC  
実行時間 1,011 ms / 3,000 ms
コード長 4,445 bytes
コンパイル時間 18,595 ms
コンパイル使用メモリ 461,228 KB
実行使用メモリ 91,896 KB
最終ジャッジ日時 2024-06-23 01:00:50
合計ジャッジ時間 64,725 ms
ジャッジサーバーID
（参考情報） 		judge1 / judge5
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ファイルパターン 結果
other AC * 58
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ソースコード

diff # 

import java.io.BufferedReader
import java.io.InputStream
import java.io.InputStreamReader
import java.util.*
import kotlin.math.abs
import kotlin.math.max
import kotlin.math.min

val MOD = 1_000_000_007L

/**
 * (dist, parent, queue)
 */
fun traceBfs(g: Array<IntArray>, rt: Int = 0): Array<IntArray> {
  val n = g.size
  val q = IntArray(n)
  val d = IntArray(n)
  val p = IntArray(n){-2}
  var cur = 0
  var last = 1
  p[rt] = -1
  q[0] = rt
  d[rt] = 0
  while (cur < last) {
    val v = q[cur++]
    for (u in g[v]) {
      if (p[u] == -2) {
        p[u] = v
        q[last++] = u
        d[u] = d[v] + 1
      }
    }
  }
  return arrayOf(d, p, q)
}
fun packUGraph(n: Int, from: IntArray, to: IntArray): Array<IntArray> {
  val p = IntArray(n)
  val m = from.size
  for (i in 0 until m) {
    ++p[from[i]]
    ++p[to[i]]
  }
  val g = Array(n){IntArray(p[it])}
  for (i in 0 until m) {
    g[from[i]][--p[from[i]]] = to[i]
    g[to[i]][--p[to[i]]] = from[i]
  }
  return g
}
class Solver(stream: InputStream, private val out: java.io.PrintWriter) {
  fun solve() {
    val N = ni()
    val (from, to) = na2(N - 1, -1)
    val g = packUGraph(N, from, to)
    val (_, par, que) = traceBfs(g)

    val pow2 = LongArray(N + 1)
    pow2[0] = 1
    for (i in 1 until pow2.size) {
      pow2[i] = pow2[i - 1] * 2 % MOD
    }

    var ans = 0L
    val dpc = IntArray(N){1}
    val dp = Array(4){LongArray(N){1} }
    for (i in N - 1 downTo 0) {
      val u = que[i]
      for (v in g[u]) {
        if (v == par[u]) continue
        dp[3][u] = dp[3][u] * dp[0][v] % MOD +
            dp[3][v] * dp[0][u] % MOD +
            3 * dp[2][v] * dp[1][u] % MOD +
            3 * dp[2][u] * dp[1][v] % MOD +
            dp[3][u] * dp[0][v] % MOD
        dp[3][u] %= MOD

        dp[2][u] = dp[2][u] * dp[0][v] % MOD +
            dp[2][v] * dp[0][u] % MOD +
            2 * dp[1][v] * dp[1][u] % MOD +
            dp[2][u] * dp[0][v] % MOD
        dp[2][u] %= MOD

        dp[1][u] = dp[1][u] * dp[0][v] % MOD +
            dp[1][v] * dp[0][u] % MOD +
            dp[1][u] * dp[0][v] % MOD
        dp[1][u] %= MOD

        dp[0][u] = dp[0][u] * dp[0][v] * 2 % MOD

        dpc[u] += dpc[v]

        debug{"$u->$v"}
      }
      debug{"$u"}
      debugDim(dp)

      val outNodes = N - dpc[u]
      ans = (ans + dp[3][u] * pow2[max(0, outNodes - 1)]) % MOD
    }

    out.println(ans)
  }













































  private val isDebug = try {
    // なんか本番でエラーでる
    System.getenv("MY_DEBUG") != null
  } catch (t: Throwable) {
    false
  }

  private var tokenizer: StringTokenizer? = null
  private val reader = BufferedReader(InputStreamReader(stream), 32768)
  private fun next(): String {
    while (tokenizer == null || !tokenizer!!.hasMoreTokens()) {
      tokenizer = StringTokenizer(reader.readLine())
    }
    return tokenizer!!.nextToken()
  }

  private fun ni() = next().toInt()
  private fun nl() = next().toLong()
  private fun ns() = next()
  private fun na(n: Int, offset: Int = 0): IntArray {
    return map(n) { ni() + offset }
  }
  private fun nal(n: Int, offset: Int = 0): LongArray {
    val res = LongArray(n)
    for (i in 0 until n) {
      res[i] = nl() + offset
    }
    return res
  }

  private fun na2(n: Int, offset: Int = 0): Array<IntArray> {
    val a  = Array(2){IntArray(n)}
    for (i in 0 until n) {
      for (e in a) {
        e[i] = ni() + offset
      }
    }
    return a
  }

  private inline fun map(n: Int, f: (Int) -> Int): IntArray {
    val res = IntArray(n)
    for (i in 0 until n) {
      res[i] = f(i)
    }
    return res
  }

  private inline fun debug(msg: () -> String) {
    if (isDebug) System.err.println(msg())
  }

  private fun debug(a: LongArray) {
    debug { a.joinToString(" ") }
  }

  private fun debug(a: IntArray) {
    debug { a.joinToString(" ") }
  }

  private fun debug(a: BooleanArray) {
    debug { a.map { if (it) 1 else 0 }.joinToString("") }
  }

  private fun debugDim(A: Array<LongArray>) {
    if (isDebug) {
      for (a in A) {
        debug(a)
      }
    }
  }
  private fun debugDim(A: Array<IntArray>) {
    if (isDebug) {
      for (a in A) {
        debug(a)
      }
    }
  }

  /**
   * 勝手にimport消されるのを防ぎたい
   */
  private fun hoge() {
    min(1, 2)
    max(1, 2)
    abs(-10)
  }
}

fun main() {
  val out = java.io.PrintWriter(System.out)
  Solver(System.`in`, out).solve()
  out.flush()
}
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