#946818 (C) No.2616 中央番目の中央値

• 問題: No.2616 中央番目の中央値
• ユーザー: chro_96
• 提出日時: 2024-01-26 23:30:52
• 言語: C (gcc 12.3.0)
• 結果: AC
• 実行時間: 131 ms / 2,000 ms
• コード長: 1,984 bytes
• コンパイル時間: 480 ms
• コンパイル使用メモリ: 31,744 KB
• 実行使用メモリ: 10,624 KB
• 最終ジャッジ日時: 2024-09-28 09:08:19
• 合計ジャッジ時間: 4,081 ms
• ジャッジサーバーID （参考情報）: judge1 / judge5

入力	結果	実行時間; 実行使用メモリ
testcase_00	AC	5 ms; 10,624 KB
testcase_01	AC	3 ms; 10,624 KB
testcase_02	AC	3 ms; 10,624 KB
testcase_03	AC	4 ms; 10,624 KB
testcase_04	AC	4 ms; 10,624 KB
testcase_05	AC	5 ms; 10,624 KB
testcase_06	AC	4 ms; 10,624 KB
testcase_07	AC	4 ms; 10,496 KB
testcase_08	AC	4 ms; 10,624 KB
testcase_09	AC	4 ms; 10,624 KB
testcase_10	AC	4 ms; 10,624 KB
testcase_11	AC	3 ms; 10,624 KB
testcase_12	AC	3 ms; 10,624 KB
testcase_13	AC	6 ms; 10,624 KB
testcase_14	AC	5 ms; 10,624 KB
testcase_15	AC	7 ms; 10,624 KB
testcase_16	AC	10 ms; 10,624 KB
testcase_17	AC	13 ms; 10,624 KB
testcase_18	AC	20 ms; 10,624 KB
testcase_19	AC	40 ms; 10,624 KB
testcase_20	AC	38 ms; 10,624 KB
testcase_21	AC	80 ms; 10,624 KB
testcase_22	AC	125 ms; 10,624 KB
testcase_23	AC	122 ms; 10,624 KB
testcase_24	AC	80 ms; 10,624 KB
testcase_25	AC	80 ms; 10,624 KB
testcase_26	AC	125 ms; 10,624 KB
testcase_27	AC	131 ms; 10,540 KB
testcase_28	AC	118 ms; 10,544 KB
testcase_29	AC	121 ms; 10,496 KB
testcase_30	AC	125 ms; 10,624 KB
testcase_31	AC	126 ms; 10,624 KB
testcase_32	AC	125 ms; 10,624 KB
testcase_33	AC	122 ms; 10,624 KB
testcase_34	AC	128 ms; 10,624 KB
testcase_35	AC	118 ms; 10,624 KB
testcase_36	AC	119 ms; 10,624 KB

ソースコード

#include <stdio.h>

long long power_mod (long long a, long long b, long long mod_num) {
  long long ans = 1LL;
  
  if (b > 0LL) {
    ans = power_mod(a, b/2LL, mod_num);
    ans = (ans * ans) % mod_num;
    if (b%2LL > 0LL) {
      ans = (ans * (a % mod_num)) % mod_num;
    }
  }
  
  return ans;
}

void add_segt (int *t, int idx, int val, int size) {
  idx = idx+size-1;
  t[idx] += val;
  
  while (idx > 0) {
    idx = (idx-1)/2;
    t[idx] += val;
  }
  
  return;
}

int sum_segt_rec (int *t, int a, int b, int k, int l, int r) {
  int ans = 0;
  
  if (r <= a || b <= l) {
    return 0;
  }
  
  if (a <= l && r <= b) {
    return t[k];
  }
  
  ans = sum_segt_rec(t, a, b, 2*k+1, l, (l+r)/2);
  ans += sum_segt_rec(t, a, b, 2*k+2, (l+r)/2, r);
  
  return ans;
}

int sum_segt (int *t, int a, int b, int size) {
  return sum_segt_rec(t, a, b, 0, 0, size);
}

int main () {
  int n = 0;
  int p = 0;
  
  int res = 0;
  
  long long ans = 0LL;
  long long mod_num = 998244353LL;
  
  int t[1048575] = {};
  int size = 1;
  
  long long fact[300001] = {};
  long long invf[300001] = {};
  
  res = scanf("%d", &n);
  while (size <= n) {
    size <<= 1;
  }
  fact[0] = 1LL;
  for (int i = 0; i < n; i++) {
    fact[i+1] = (fact[i]*((long long)(i+1)))%mod_num;
  }
  invf[n] = power_mod(fact[n], mod_num-2LL, mod_num);
  for (int i = n; i > 0; i--) {
    invf[i-1] = (invf[i]*((long long)i))%mod_num;
  }
  for (int i = 0; i < n; i++) {
    int llc = 0;
    int lgc = 0;
    int rlc = 0;
    int rgc = 0;
    long long tmp1 = 0LL;
    long long tmp2 = 0LL;
    res = scanf("%d", &p);
    p--;
    llc = sum_segt(t, 0, p, size);
    lgc = i-llc;
    rlc = p-llc;
    rgc = n-p-1-lgc;
    tmp1 = (fact[llc+rgc]*invf[llc])%mod_num;
    tmp1 *= invf[rgc];
    tmp1 %= mod_num;
    tmp2 = (fact[lgc+rlc]*invf[lgc])%mod_num;
    tmp2 *= invf[rlc];
    tmp2 %= mod_num;
    ans += (tmp1*tmp2)%mod_num;
    add_segt(t, p, 1, size);
  }
  
  printf("%lld\n", ans%mod_num);
  return 0;
}