Submission #1208337

#	Time	Username	Problem	Language	Result	Execution time	Memory
1208337		Gabp	Arranging Shoes (IOI19_shoes)	C++20	100 / 100	136 ms	138576 KiB

shoes

#include<bits/stdc++.h>
using namespace std;

long long int count_swaps(vector<int> S) {
  int n = S.size() / 2;
  
  int cnt = 0;
  vector<queue<int>> lIdx(n + 1), rIdx(n + 1);
  for (int i = 0; i < 2 * n; i++) {
    int x = abs(S[i]);
    if (S[i] < 0) {
      if (rIdx[x].size()) {
        int id = rIdx[x].front(); rIdx[x].pop();
        S[i] = 2 * id;
      } else {
        lIdx[x].push(cnt);
        S[i] = 2 * cnt;
        cnt++;
      }
    } else {
      if (lIdx[x].size()) {
        int id = lIdx[x].front(); lIdx[x].pop();
        S[i] = 2 * id + 1;
      } else {
        rIdx[x].push(cnt);
        S[i] = 2 * cnt + 1;
        cnt++;
      }
    }
  }
  
  long long int ans = 0;
  auto solve = [&](auto self, int l, int r) -> void {
    if (l == r) return;
    
    int mid = l + (r - l) / 2;
    self(self, l, mid);
    self(self, mid + 1, r);
    
    int p1 = l, p2 = mid + 1;
    vector<int> a;
    while (p1 <= mid || p2 <= r) {
       if (p1 > mid) a.push_back(S[p2++]);
       else if (p2 > r) a.push_back(S[p1++]);
       else if (S[p1] < S[p2]) a.push_back(S[p1++]);
       else {
        a.push_back(S[p2++]);
        ans += mid + 1 - p1;
       }
    }
    
    for (int i = l; i <= r; i++) S[i] = a[i - l];
  };
  
  solve(solve, 0, 2 * n - 1);
  
  return ans;
}

• Subtask 1: 10 / 10
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 15 / 15
• Subtask 5: 20 / 20
• Subtask 6: 15 / 15