Submission #1022681

#	Time	Username	Problem	Language	Result	Execution time	Memory
1022681		CodeAssignment	Arranging Shoes (IOI19_shoes)	C++17	100 / 100	123 ms	29012 KiB

shoes

#include <bits/stdc++.h>
#include <bits/extc++.h>

using namespace std;
using namespace __gnu_pbds;

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define trav(a, x) for (auto &a : x)
#define pb push_back
#define el "\n";
//#define dbg(x) cerr << "\e[92m" << #x << " = " << x << "\e[97m" << el;
#define dbg(x)  
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

template<class T>
using Tree = tree<T, null_type, less<T>, rb_tree_tag,
    tree_order_statistics_node_update>;

void example() {
	Tree<int> t, t2; t.insert(8);
	auto it = t.insert(10).first;
	assert(it == t.lower_bound(9));
	assert(t.order_of_key(10) == 1);
	assert(t.order_of_key(11) == 2);
	//assert(t.order_of_key(9) == 1);
	assert(*t.find_by_order(0) == 8);
	t.join(t2);
}

/* dies on
4
1 2 1 -1 -2 -1 3 -3
*/

ll count_swaps(vector<int> S) {

	/*
	auto dbgarray = [&](vi &arr, string s) -> void {
		cerr << s << " is: ";
		rep(i, 0, sz(arr)) {
			cerr << arr[i] << " ";
		}
		cerr << el;
	};
	*/

	Tree<ll> t;

	assert(sz(S) % 2 == 0);
	ll n = sz(S) / 2; // number of pairs
	vi a = S;

	vector<set<ll>> pos(2 * n + 1);
	rep(i, 0, 2*n) {
		pos[a[i] + n].insert(i);
	}

	vector<bool> done(2 * n);
	ll ans = 0;
	ll ind = 0;
	while(ind < 2 * n) {
		if (done[ind]) {
			ind++;
			continue;
		}
		ll cur = a[ind];
		auto nxt = pos[-cur + n].upper_bound(ind);
		ll bigger = t.order_of_key(-(*nxt));
		ll bigger2 = t.order_of_key(-ind);
		dbg(bigger);
		dbg(bigger2);

		assert(nxt != pos[-cur + n].end());
		assert(a[*nxt] == -cur);

		dbg(ind); dbg(cur); dbg(*nxt); dbg(a[*nxt]); dbg(sz(pos[-cur + n]));
		trav(x, pos[-cur +n]) {
			ll tmp = x;
			dbg(tmp);
		}

		ans += (*nxt) - ind - (cur < 0 ? 1 : 0) + bigger - bigger2;
		dbg(ans);


		t.insert(-(*nxt));
		pos[-cur + n].erase(*nxt);
		done[ind] = 1;
		done[*nxt] = 1;
		// TODO: we aren't actually updating the array, so how do we handle ind
		ind++;

		/*
		vi temp;
		rep(i, 0, ind) {
			temp.pb(a[i]);
		}
		temp.pb((cur < 0 ? cur : -cur));
		temp.pb((cur < 0 ? -cur : cur));
		rep(i, ind + 1, 2*n)  {
			if (i == *nxt) continue;
			temp.pb(a[i]);
		}
		assert(sz(temp) == 2 * n);
		swap(a, temp);
		*/

	}
	return ans;
}

Compilation message (stderr)

shoes.cpp: In function 'll count_swaps(std::vector<int>)':
shoes.cpp:83:7: warning: unused variable 'tmp' [-Wunused-variable]
   83 |    ll tmp = x;
      |       ^~~

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