Submission #1279165

#	Time	Username	Problem	Language	Result	Execution time	Memory
1279165		lazylettuce	Arranging Shoes (IOI19_shoes)	C++20	45 / 100	185 ms	32612 KiB

shoes

// _                 _      _   _                  
//| | __ _ _____   _| | ___| |_| |_ _   _  ___ ___ 
//| |/ _` |_  / | | | |/ _ \ __| __| | | |/ __/ _ \lazylettuce
//| | (_| |/ /| |_| | |  __/ |_| |_| |_| | (_|  __/
//|_|\__,_/___|\__, |_|\___|\__|\__|\__,_|\___\___|
//             |___/                               
#include<bits/stdc++.h>

using namespace std;
using ll =long long ;
int MOD1=998244353;
int MOD2=1e9+7;

struct Fenwick {
    int n;
    vector<ll> bit;
    Fenwick(int n_ = 0) { init(n_); }
    void init(int n_) { n = n_; bit.assign(n+1, 0); }
    void update(int idx, ll delta = 1) {
        if (idx <= 0) return;
        for (; idx <= n; idx += idx & -idx) bit[idx] += delta;
    }
    ll query(int idx) {
        if (idx <= 0) return 0;
        ll res = 0;
        for (; idx > 0; idx -= idx & -idx) res += bit[idx];
        return res;
    }
    ll total() { return query(n); }
    ll inv_count(const vector<int>& v) {
        fill(bit.begin(), bit.end(), 0);
        ll inv = 0;
        for (int x : v) {
            if (x < 1 || x > n) {
                // skip bad indices (defensive)
                continue;
            }
            inv += (total() - query(x));
            update(x, 1);
        }
        return inv;
    }
};


long long count_swaps(std::vector<int> S) {
    int m = S.size();
    std::map<int, std::set<int>> left_indices, right_indices;

    for (int i = 0; i < m; i++) {
        if (S[i] < 0) {
            left_indices[abs(S[i])].insert(i + 1);
        } else {
            right_indices[abs(S[i])].insert(i + 1);
        }
    }

    std::vector<int> temp; 

    for (int i = 0; i < m; ++i) {
        if (S[i] < 0) {
            int mag = abs(S[i]);
            
            auto it = right_indices[mag].begin();
            int right_partner_idx = *it;

            temp.push_back(i + 1); 
            temp.push_back(right_partner_idx);

            right_indices[mag].erase(it);
        }
    }

    Fenwick f(m);
    ll ans = f.inv_count(temp);
    return ans;
}

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