Submission #766689

#	Time	Username	Problem	Language	Result	Execution time	Memory
766689		t6twotwo	Arranging Shoes (IOI19_shoes)	C++17	10 / 100	1 ms	212 KiB

shoes

#include "shoes.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll count_swaps(vector<int> s) {
    int n = s.size() / 2;
    vector<int> bit(2 * n + 1);
    auto add = [&](int p, int v) {
        for (int i = p + 1; i <= 2 * n; i += i & -i) {
            bit[i] += v;
        }
    };
    auto sum = [&](int p) {
        int ans = 0;
        for (int i = p; i > 0; i -= i & -i) {
            ans += bit[i];
        }
        return ans;
    };
    ll ans = 0;
    vector<int> a[2];
    for (int i = 0; i < 2 * n; i++) {
        int q = s[i] > 0;
        if (!a[!q].empty()) {
            int p = a[!q].back();
            a[!q].pop_back();
            ans += (i - p - 1) - (sum(i) - sum(p)) + !q;
            add(i, 1);
            add(p, -1);
        } else {
            a[q].push_back(i);
        }
    }
    return ans;
}

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