Submission #476746

#	Time	Username	Problem	Language	Result	Execution time	Memory
476746		ponytail	Arranging Shoes (IOI19_shoes)	C++17	30 / 100	701 ms	162308 KiB

shoes

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 5;
typedef long long ll;
int n;
int inv(int x){
    if(x<0) return -x;
    else if(x>n) return x - n;
    else return x + n;
}
ll same_size(vector<int> S) {
    ll ans1 = 0, ans2 = 0;
    n = S.size() / 2;
    map<int, queue<int> > mp;
    int nxt = 0;
    for(int i=0; i<2*n; i++) {
        if(mp[inv(S[i])].size()){
            ans1 += abs(mp[inv(S[i])].front() - nxt) + abs(i - nxt - 1);
            ans2 += (S[i]<0);
            nxt += 2;
            mp[inv(S[i])].pop();
        }
        else{
            mp[inv(inv(S[i]))].push(i);
        }
    }
    return ans1 / 2 + ans2;
}
ll count_swaps(vector<int> S){
    map<int, vector<int> > mp;
    for(int i=0; i<S.size(); i++) {
        mp[abs(S[i])].push_back(S[i]);
    }
    ll ans = 0;
    for(auto x: mp) {
        ans += same_size(x.second);
    }
    map<int, int> freq;
    for(int i=0; i<S.size(); i++) {
        if(freq[abs(S[i])] & 1) S[i] = abs(S[i]);
        else S[i] = -abs(S[i]);
        freq[abs(S[i])]++;
    }
    ans += same_size(S);
    return ans;
}
mt19937 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
void solve() {
    int n; //= uniform_int_distribution<int>(1, 4)(rng); 
    cin >> n;
    vector<int> v(2*n);
    for(int i=0; i<2*n; i++) cin >> v[i]; //v[i] = (i < n ? i+1 : -(i+1-n));
    //shuffle(v.begin(), v.end(), rng);
    cout << count_swaps(v) << "\n";
}

Compilation message (stderr)

shoes.cpp: In function 'll count_swaps(std::vector<int>)':
shoes.cpp:31:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |     for(int i=0; i<S.size(); i++) {
      |                  ~^~~~~~~~~
shoes.cpp:39:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |     for(int i=0; i<S.size(); i++) {
      |                  ~^~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 0 / 20
• Subtask 3: 20 / 20
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 15