#512775 (C++17) No.1115 二つの数列 / Two Sequences

• 問題: No.1115 二つの数列 / Two Sequences
• ユーザー: emthrm
• 提出日時: 2020-07-17 21:30:39
• 言語: C++17 (gcc 13.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 47 ms / 2,000 ms
• コード長: 2,481 bytes
• コンパイル時間: 2,034 ms
• コンパイル使用メモリ: 201,508 KB
• 最終ジャッジ日時: 2025-01-11 22:13:42
• ジャッジサーバーID （参考情報）: judge5 / judge5

ファイルパターン	結果
sample	AC * 5
other	AC * 35

ソースコード

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#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-8;
const int MOD = 1000000007;
// const int MOD = 998244353;
const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
const int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  }
} iosetup;
template <typename Abelian>
struct BIT0based {
  BIT0based(int n, const Abelian UNITY = 0) : n(n), UNITY(UNITY), dat(n, UNITY) {}
  void add(int idx, Abelian val) {
    while (idx < n) {
      dat[idx] += val;
      idx |= idx + 1;
    }
  }
  Abelian sum(int idx) const {
    Abelian res = UNITY;
    --idx;
    while (idx >= 0) {
      res += dat[idx];
      idx = (idx & (idx + 1)) - 1;
    }
    return res;
  }
  Abelian sum(int left, int right) const {
    return left < right ? sum(right) - sum(left) : UNITY;
  }
  Abelian operator[](const int idx) const { return sum(idx, idx + 1); }
  int lower_bound(Abelian val) const {
    if (val <= UNITY) return 0;
    int res = 0, exponent = 1;
    while (exponent <= n) exponent <<= 1;
    for (int mask = exponent >> 1; mask > 0; mask >>= 1) {
      if (res + mask - 1 < n && dat[res + mask - 1] < val) {
        val -= dat[res + mask - 1];
        res += mask;
      }
    }
    return res;
  }
private:
  int n;
  const Abelian UNITY;
  vector<Abelian> dat;
};
template <typename T>
ll inversion_number(const vector<T> &a) {
  int n = a.size();
  vector<T> comp(a);
  sort(ALL(comp));
  comp.erase(unique(ALL(comp)), comp.end());
  BIT0based<int> bit(comp.size());
  ll res = 0;
  REP(i, n) {
    int idx = lower_bound(ALL(comp), a[i]) - comp.begin();
    res += i - bit.sum(idx);
    bit.add(idx, 1);
  }
  return res;
}
int main() {
  int n; cin >> n;
  vector<int> pos(n);
  REP(i, n) {
    int a; cin >> a; --a;
    pos[a] = i;
  };
  vector<int> a(n);
  REP(i, n) {
    int b; cin >> b; --b;
    a[pos[b]] = i;
  }
  cout << inversion_number(a) << '\n';
  return 0;
}
 
 
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