Submission #1210781

#	Time	Username	Problem	Language	Result	Execution time	Memory
1210781		madamadam3	Arranging Shoes (IOI19_shoes)	C++20	45 / 100	51 ms	11332 KiB

shoes

#include "shoes.h"
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

uint64_t hash_vec(const vector<int> &inp) {
	const uint64_t BASE = 998244353;
	uint64_t h = 0;
	for (int x : inp) {
		h = h * BASE + (uint32_t)x + 1;
	}

	return h;
}

int n;

struct State {
	vector<pair<int, int>> swaps;
	vector<int> arr;
	int moves;
	int p1, p2;
};

bool check_valid(State &state, vector<int> &initial) {
	vector<int> arrangement = initial;
	for (auto &el : state.swaps) {
		swap(arrangement[el.first], arrangement[el.second]);
	}

	bool valid = true;
	for (int i = 0; i < n; i++) {
		valid = valid && (abs(arrangement[2*i]) == abs(arrangement[2*i+1])) && (arrangement[2*i] < 0 && arrangement[2*i+1] > 0);
	}
	return valid;
}

bool check_valid(vector<int> &arrangement) {
	bool valid = true;
	for (int i = 0; i < n; i++) {
		valid = valid && (abs(arrangement[2*i]) == abs(arrangement[2*i+1])) && (arrangement[2*i] < 0 && arrangement[2*i+1] > 0);
	}
	return valid;
}

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

	// if all shoes are same size:
	// find how many swaps to make each right shoe occupy an odd position
	// this forces each left shoe to occupy an even position
	
	set<int> avail; // available odd positions
	set<int> right_shoes;

	for (int i = 1; i < 2*n; i+=2) avail.insert(i);
	for (int i = 0; i < 2 * n; i++) {
		int el = s[i];
		if (el < 0) continue;

		if (i % 2 == 1) avail.erase(i);
		else right_shoes.insert(i);
	}

	while (!avail.empty()) {
		int f1 = *avail.begin(), f2 = *right_shoes.begin();
		minimum += abs(f1 - f2);
		avail.erase(f1);
		right_shoes.erase(f2);
	}

	return minimum;
}

// left shoe if s[i] < 0
// right shoe if s[i] > 0
// ll count_swaps(vector<int> s) {
// 	n = s.size() / 2;
// 	int minimum = 0;

// 	queue<State> q;
// 	State best;

// 	q.push(State{{}, s, 0, -1, -1});
// 	unordered_set<uint64_t> vis;
// 	vis.insert(hash_vec(s));

// 	while (!q.empty()) {
// 		State cur = q.front();
// 		q.pop();

// 		// if (check_valid(cur, s)) {
// 		if (check_valid(cur.arr)) {
// 			minimum = cur.moves;
// 			best = cur;
// 			break;
// 		}

// 		for (int i = 1; i < 2*n; i++) {
// 			for (int j = i-1; j < i+2 && j < 2*n; j++) {
// 				if (i == j) continue;
// 				if (((i == cur.p1) && (j == cur.p2)) || ((j == cur.p1) && (i == cur.p2))) continue;
// 				// vector<pair<int, int>> swaps = cur.swaps;
// 				// swaps.push_back({i, j});
// 				// q.push(State{swaps, cur.moves + 1, i, j});

// 				vector<int> cs = cur.arr;
// 				swap(cs[i], cs[j]);
// 				uint64_t h = hash_vec(cs);
// 				if (vis.count(h)) continue;
// 				vis.insert(h);

// 				q.push(State{{}, cs, cur.moves + 1, i, j});
// 			}
// 		}
// 	}
	
// // 	cout << "Fastest fix is " << best.moves << " moves\n";
// // 	for (auto &el : best.swaps) {
// // 		cout << "Swapped " << el.first << " and " << el.second << "\n";
// // 	}
// 	return minimum;
// 	// return ll(n) * ll(n - 1) / 2LL;
// }

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