Submission #6941357

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Source Code Expand

#include <bits/stdc++.h>

// Begin {{{
using namespace std;

#define all(x) x.begin(), x.end()
#define rep(i, n) for (i64 i = 0; i < (n); ++i)
#define reps(i, s, n) for (i64 i = (s); i <= (n); ++i)

using i64 = int_fast64_t;
using pii = pair<i64, i64>;

template<class A, class B>
inline bool chmax(A &a, const B &b) { return b > a ? a = b, 1 : 0; }

template<class A, class B>
inline bool chmin(A &a, const B &b) { return b < a ? a = b, 1 : 0; }

constexpr int INF = 0x3f3f3f3f;
constexpr i64 LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr int MOD = int(1e9) + 7;

//IN
void IN() {}
template<class Head, class... Tail>
void IN(Head&& head, Tail&&... tail) {
  cin >> head;
  IN(forward<Tail>(tail)...);
}

//OUTS
template<size_t> struct int_{};
template<class Tuple, size_t Pos>
ostream& print_tuple(ostream& out, const Tuple& t, int_<Pos>) {
  out << get<tuple_size<Tuple>::value-Pos>(t) << " ";
  return print_tuple(out, t, int_<Pos-1>());
}

template <class Tuple>
ostream& print_tuple(ostream& out, const Tuple& t, int_<1>) {
  return out << get<tuple_size<Tuple>::value-1>(t);
}

template<class... Args>
ostream& operator<<(ostream& out, const tuple<Args...>& t) {
  return print_tuple(out, t, int_<sizeof...(Args)>());
}

#define OUTS(...) cout << make_tuple(__VA_ARGS__) << "\n";

//OUTL
void OUTL() {}
template<class Head, class... Tail>
void OUTL(Head&& head, Tail&&... tail) {
  cout << head << "\n";
  OUTL(forward<Tail>(tail)...);
}
// }}} End

signed main()
{
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int n;
  IN(n);

  i64 res = 0;
  map<int, int> mp;
  reps(i, 1, n) {
    int a; IN(a);
    mp[i] = a;
    if (mp[a] == i) ++res;
  }

  OUTL(res);

  return 0;
}

Submission Info

Judge Result