# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
411800 | timmyfeng | Arranging Shoes (IOI19_shoes) | C++17 | 0 ms | 0 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#include <bits/extc++.h>
template <class T, class Comp = less<T>>
using ordered_set = __gnu_pbds::tree<
T, __gnu_pbds::null_type, Comp,
__gnu_pbds::rb_tree_tag,
__gnu_pbds::tree_order_statistics_node_update
>;
long long count_swaps(vector<int> s) {
int n = s.size() / 2;
map<int, vector<int>> nxt;
ordered_set<int> shoes;
for (int i = 2 * n - 1; i >= 0; --i) {
nxt[s[i]].push_back(i);
shoes.insert(i);
}
long long ans = 0;
while (!shoes.empty()) {
auto i = *shoes.begin();
shoes.erase(shoes.begin());
int x = s[i];
nxt[x].pop_back();
int j = nxt[-x].back();
nxt[-x].pop_back();
ans += shoes.order_of_key(j) + (x > 0);
shoes.erase(j);
}
return ans;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin >> n;
vector<int> s(2 * n);
for (int i = 0; i < 2 * n; ++i) {
cin >> s[i];
}
cout << count_swaps(s) << "\n";
}