Submission #143267

#	Time	Username	Problem	Language	Result	Execution time	Memory
143267		tpoppo	Arranging Shoes (IOI19_shoes)	C++14	100 / 100	229 ms	141008 KiB

shoes

#include "shoes.h"
#include<bits/stdc++.h>
#define lsb(x) (x&(-x))

using namespace std;

const int MAXN = 2e5 + 1000;
const int OFFSET = 1e5 + 50;
using pii = pair<int,int>;
using ll = long long;
struct fenwick{
  int N;
  vector<ll> ft;
  void init(int n){
      N=n;
      ft.resize(n+1);
  }

  void update(int pos,int delta){
      for(++pos;pos<=N;pos+=lsb(pos)){
          ft[pos]+=delta;
      }
  }
  ll query(int pos){
      ll ans=0;
      for(++pos;pos!=0;pos-=lsb(pos)){
          ans+=ft[pos];
      }
      return ans;
  }
  ll sum(int a,int b){
      return query(b)-query(a-1);
  }

  void debug(){
      for(int i=0;i<N;i++){
          cout<<i<<" "<<query(i)<<endl;
      }
  }
};


deque<int> comb[MAXN];
fenwick ft;
vector<pii> cp;
int v[MAXN];

ll res = 0;
long long count_swaps(std::vector<int> s) {

  for(int i=0;i<s.size();i++){
    int val = s[i];
    if(comb[val + OFFSET].empty()){
      comb[OFFSET - val].push_back(i);
    }else{
      if(s[i] < 0) cp.emplace_back(i,comb[val + OFFSET].front());
      else cp.emplace_back(comb[val + OFFSET].front(),i);
      comb[val + OFFSET].pop_front();
    }
  }

  sort(cp.begin(),cp.end(),[](pii a,pii b){ return a.first + a.second < b.first + b.second;});

  for(int i=0;i<cp.size();i++){
    v[2*i] = cp[i].first;
    v[2*i+1] = cp[i].second;
  }

  ft.init(2*cp.size());
  for(int i=0;i<2*cp.size();i++){
    //cout<<v[i]<< " " << s[v[i]] <<endl;
    res += i - ft.query(v[i]);
    ft.update(v[i],1);
  }
	return res;
}

Compilation message (stderr)

shoes.cpp: In function 'long long int count_swaps(std::vector<int>)':
shoes.cpp:51:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<s.size();i++){
               ~^~~~~~~~~
shoes.cpp:64:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<cp.size();i++){
               ~^~~~~~~~~~
shoes.cpp:70:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<2*cp.size();i++){
               ~^~~~~~~~~~~~

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