Submission #532981

#TimeUsernameProblemLanguageResultExecution timeMemory
532981andecaandeciArranging Shoes (IOI19_shoes)C++17
10 / 100
57 ms13612 KiB
#include <bits/stdc++.h>
using namespace std;

template <typename T>
struct Fenwick {
    vector<T> t;
    T n;
    Fenwick(T n) : n(n) {
        t.resize(n);
    }
    T g(T r){
        T ret = 0;
        for (; r >= 0; r = (r & (r + 1)) - 1)
            ret += t[r];
        return ret;
    }
    T sum(T l, T r){
        return g(r) - g(l - 1);
    }
    void add(T i, T v){
        for(;i < n; i = i | (i + 1))
            t[i] += v;
    }

    void range_add(T l, T r, T v){
      add(l, v);
      add(r + 1, -v);
    }
};

long long count_swaps(vector<int> s){
  long long n = s.size(), ans = 0;
  const int N = 1e5;
  vector<int> p[2 * N + 100];
  for(int i=0;i<n;i++)
  {
    p[s[i] + N].push_back(i);
  }
  Fenwick<int> fw(n + 100);
  vector<bool> vis(n);
  for(int i=0;i<n;i++)
  {
    if(vis[i]) continue;
    auto it = lower_bound(p[-s[i] + N].begin(), p[-s[i] + N].end(), i + 1);
    // cout << (pos + fw.g(pos)) - (i + 1 + fw.g(i + 1)) << '\n';
    if(it == p[-s[i] + N].end()) continue;
    int pos = *it;
    ans += (pos + fw.g(pos)) - (i + 1 + fw.g(i + 1)); 
    vis[pos] = 1;
    vis[i] = 1;
    fw.range_add(i+1, pos, 1);
    if(s[i] > s[pos])
    {
      ans += 1;
    }
  }
  return ans;
}

// signed main(){
//   int n;
//   cin >> n;
//   vector<int> t(2*n);
//   for(int i=0;i<2*n;i++) cin >> t[i];
//   cout << count_swaps(t) << '\n';
// }
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