Submission #976798

#	Time	Username	Problem	Language	Result	Execution time	Memory
976798		efedmrlr	Arranging Shoes (IOI19_shoes)	C++17	100 / 100	193 ms	27816 KiB

shoes

#include <bits/stdc++.h>
#include "shoes.h"

#define lli long long int
#define ld long double
#define pb push_back
#define MP make_pair
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define REP(i, n) for(int i = 0; (i) < (n); (i)++)

using namespace std;

void fastio() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
}

const int N = 1e5 + 5;
const int INF = 1e9 + 500;

struct Fenwick {
    vector<int> st;
    int n;
    void init(int nn) {
        n = nn;
        st.assign(n + 3, 0);
    }

    void update(int ind, int val) {
        ind++;
        while(ind <= n) {
            st[ind] += val;
            ind += (ind) & (-ind);
        }
    }
    int getSum(int ind) {
        ind++;
        int ret = 0;
        while(ind > 0) {
            ret += st[ind];
            ind -= ind & (-ind);
        }
        return ret;
    }
};

long long count_swaps(std::vector<int> s) {
    int n = (int)s.size() / 2;

    map<int, vector<int> > occ;
    for(int i = 0; i < 2*n; i++) {
        occ[s[i]].pb(i);
    }
    vector<array<int, 2> > pr;

    for(int i = 1; i <= n; i++) {
        auto &x = occ[i];
        auto &y = occ[-i];

        for(int j = 0; j < x.size(); j++) {
            pr.pb({y[j], x[j]});
        }
    }
    vector<int> ord(2 * n, 0);
    sort(all(pr), [](array<int, 2> &x, array<int, 2> &y) {
        return x[0] + x[1] < y[0] + y[1];
    });
    
    for(int i = 0; i < n; i++) {
        ord[pr[i][0]] = i * 2;
        ord[pr[i][1]] = i * 2 + 1;
    }
    lli inv = 0;
    Fenwick st;
    st.init(2 * n + 1);
    for(int i = 2 * n - 1; i >= 0; i--) {
        inv += st.getSum(ord[i]);
        st.update(ord[i], 1);
    }
    return inv;
}

Compilation message (stderr)

shoes.cpp: In function 'long long int count_swaps(std::vector<int>)':
shoes.cpp:61:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |         for(int j = 0; j < x.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