Submission #718862

#	Time	Username	Problem	Language	Result	Execution time	Memory
718862		Yell0	Arranging Shoes (IOI19_shoes)	C++17	100 / 100	75 ms	16416 KiB

shoes

#include <bits/stdc++.h>
 
using namespace std;
const int MN=1e5+2;
typedef long long ll;
struct bit {
  vector<int> arr;
  bit(int sz) {
    arr=vector<int>(sz,0);
  }
  void upd(int i,int v) {
    for(;i<arr.size();i+=-i&i) arr[i]+=v;
  }
  int qry(int i) {
    int ret=0;
    for(;i>0;i-=-i&i) ret+=arr[i];
    return ret;
  }
};

ll count_swaps(vector<int> S) {
  ll N=S.size()/2,ans=0,sub=0;
  bit bit(N*2+2);
  vector<int> sti(N*2+2,0),edi(N*2+2,0);
  S.insert(S.begin(),0);
  vector<vector<int>> pos(2*MN);
  for(int i=1;i<=2*N;++i) pos[S[i]+N].push_back(i);
  for(int i=0;i<N;++i)
    for(int j=0;j<pos[i].size();++j) {
      ans+=(pos[N+N-i][j]<pos[i][j]);
      int f=min(pos[N+N-i][j],pos[i][j]),s=max(pos[N+N-i][j],pos[i][j]);
      sti[s]=f;
      edi[f]=s;
    }
  for(int i=1;i<=2*N;++i) {
    if(sti[i]) {
      bit.upd(sti[i],-2);
      if(sti[i]==i-1) {
        bit.upd(sti[i],1);
        continue; 
      }
      ans+=i-sti[i]-1;
      sub+=bit.qry(i)-bit.qry(sti[i]);
      bit.upd(i,1);
    } else bit.upd(i,1);
  }
  return ans-sub/2;
}

Compilation message (stderr)

shoes.cpp: In member function 'void bit::upd(int, int)':
shoes.cpp:12:11: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |     for(;i<arr.size();i+=-i&i) arr[i]+=v;
      |          ~^~~~~~~~~~~
shoes.cpp: In function 'll count_swaps(std::vector<int>)':
shoes.cpp:29:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |     for(int j=0;j<pos[i].size();++j) {
      |                 ~^~~~~~~~~~~~~~

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