Submission #1004609

#	Time	Username	Problem	Language	Result	Execution time	Memory
1004609		phoenix	Sorting (IOI15_sorting)	C++17	100 / 100	181 ms	20284 KiB

sorting

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

using namespace std;



int findSwapPairs(int n, int S[], int m, int X[], int Y[], int P[], int Q[]) {
	vector<pair<int, int>> res;
	
	function<bool(int)> check = [&](int len) -> bool {
		res.resize(len);
		vector<int> s(n), pos(n);
		for (int i = 0; i < n; i++) {
			s[i] = S[i];
			pos[S[i]] = i;
		}

		vector<int> p(n), q(n);
		iota(p.begin(), p.end(), 0);
		iota(q.begin(), q.end(), 0);
		auto do_swap = [&](int i, int j) {
			swap(p[i], p[j]);
			swap(q[p[i]], q[p[j]]);
		};
		for (int i = len - 1; i >= 0; i--) {
			do_swap(X[i], Y[i]);
		}

		int l = n - 1;
		for (int i = 0; i < len; i++) {
			do_swap(X[i], Y[i]);
			swap(s[X[i]], s[Y[i]]);
			swap(pos[s[X[i]]], pos[s[Y[i]]]);

			while (l >= 0 && q[l] == pos[l]) 
				l--;
			if (l == -1) 
				res[i] = {0, 0};
			else {
				res[i] = {pos[l], q[l]};
			}
			swap(s[res[i].first], s[res[i].second]);
			swap(pos[s[res[i].first]], pos[s[res[i].second]]);
		}
		while (l >= 0 && q[l] == pos[l]) l--;
		return (l == -1);
	};

	int l = -1, r = m + 1;
	while (r - l > 1) {
		int mid = (l + r) / 2;
		if (check(mid)) 
			r = mid;
		else 
			l = mid;
	}
	check(r);
	for (int i = 0; i < r; i++) {
		P[i] = res[i].first;
		Q[i] = res[i].second;
	}
	return r;
}

• Subtask 1: 8 / 8
• Subtask 2: 12 / 12
• Subtask 3: 16 / 16
• Subtask 4: 18 / 18
• Subtask 5: 20 / 20
• Subtask 6: 26 / 26