Submission #487116

#	Time	Username	Problem	Language	Result	Execution time	Memory
487116		Spade1	Arranging Shoes (IOI19_shoes)	C++17	100 / 100	61 ms	13552 KiB

shoes

#include <bits/stdc++.h>
#include "shoes.h"
#define ll long long
#define pii pair<int, int>
#define st first
#define nd second
#define pb push_back
using namespace std;

int fw[200020];
vector<pii> pos[200020];
vector<pii> swp;

void update(int i, int val) {
    for (; i <= 200000; i += i&-i) {
        fw[i] += val;
    }
}

int query(int i) {
    int cnt = 0;
    for (; i > 0; i -= i&-i) {
        cnt += fw[i];
    }
    return cnt;
}

ll count_swaps(vector<int> s) {
    int n = s.size()/2;
    s.insert(s.begin(), 0);

    ll ans = 0;
    for (int i = 1; i <= 2*n; ++i) {
        update(i, 1);
        pos[abs(s[i])].pb({s[i], i});
    }

    for (int i = 1; i <= n; ++i) {
        sort(pos[i].begin(), pos[i].end());
        int m = pos[i].size();
        for (int j = 0; j < m/2; ++j) {
            int l = pos[i][j].nd;
            int r = pos[i][j + m/2].nd;
            if (l > r) {
                ++ans;
                swap(l, r);
            }
            swp.pb({l, r});
        }
    }

    sort(swp.begin(), swp.end());

    for (auto [l, r] : swp) {
        ans += query(r - 1) - query(l);
        update(r, -1);
        update(l, -1);
    }

    return ans;
}

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