結果

問題 No.271 next_permutation (2)
コンテスト
ユーザー hos.lyric
提出日時 2019-01-18 06:29:31
言語 D
(dmd 2.109.1)
結果
AC  
実行時間 36 ms / 2,000 ms
コード長 3,117 bytes
コンパイル時間 788 ms
コンパイル使用メモリ 117,724 KB
実行使用メモリ 13,420 KB
最終ジャッジ日時 2024-06-13 02:55:33
合計ジャッジ時間 1,884 ms
ジャッジサーバーID
（参考情報） 		judge1 / judge2
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ファイルパターン 結果
other AC * 21
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ソースコード

diff # 

import std.conv, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.range, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken().to!int; }
long readLong() { return readToken().to!long; }
real readReal() { return readToken().to!real; }

void chmin(T)(ref T t, in T f) { if (t > f) t = f; }
void chmax(T)(ref T t, in T f) { if (t < f) t = f; }

int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = cast(int)(as.length); for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; }
int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a < val)); }
int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a <= val)); }


immutable MO = 1000000007L;
immutable LIM = 2 * 10^^5 + 10;

long[] inv, fac, invFac;
void prepare() {
  inv = new long[LIM];
  fac = new long[LIM];
  invFac = new long[LIM];
  inv[1] = 1;
  foreach (i; 2 .. LIM) {
    inv[i] = MO - (MO / i) * inv[cast(size_t)(MO % i)] % MO;
  }
  fac[0] = invFac[0] = 1;
  foreach (i; 1 .. LIM) {
    fac[i] = (fac[i - 1] * i) % MO;
    invFac[i] = (invFac[i - 1] * inv[i]) % MO;
  }
}

void add(int[] bit, int pos, int val) {
  for (int x = pos; x < bit.length; x |= x + 1) {
    bit[x] += val;
  }
}
int getSum(int[] bit, int pos) {
  int ret;
  for (int x = pos - 1; x >= 0; x = (x & (x + 1)) - 1) {
    ret += bit[x];
  }
  return ret;
}

int N;
long K;
int[] P;

long[] total;

long calc(long[] a) {
  long ret;
  long num = 0;
  foreach_reverse (i; 0 .. N) {
    (ret += total[N - 1 - i] * a[i]) %= MO;
    (ret += fac[N - 1 - i] * a[i] % MO * (a[i] - 1) % MO * inv[2]) %= MO;
    (ret += num * a[i]) %= MO;
    (num += fac[N - 1 - i] * a[i]) %= MO;
  }
  return ret;
}

void main() {
  prepare();
  
  try {
    for (; ; ) {
      N = readInt();
      K = readLong();
      P = new int[N];
      foreach (i; 0 .. N) {
        P[i] = readInt() - 1;
      }
      
      total = new long[N + 1];
      foreach (n; 0 .. N + 1) {
        total[n] = fac[n] * n % MO * (n - 1) % MO * inv[4] % MO;
      }
      
      auto a = new long[N];
      auto bit = new int[N];
      foreach (i; 0 .. N) {
        bit.add(i, +1);
      }
      foreach (i; 0 .. N) {
        a[i] = bit.getSum(P[i]);
        bit.add(P[i], -1);
      }
      debug {
        writeln("a = ", a);
      }
      
      long ans;
      ans -= calc(a);
      
      a[N - 1] += K;
      foreach_reverse (i; 1 .. N) {
        a[i - 1] += a[i] / (N - i);
        a[i] %= (N - i);
      }
      const b = a[0] / N;
      a[0] %= N;
      debug {
        writeln("a = ", a);
        writeln("b = ", b);
      }
      ans += calc(a);
      ans += total[N] * (b % MO);
      
      ans = (ans % MO + MO) % MO;
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}
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