Submission #302506

#	Time	Username	Problem	Language	Result	Execution time	Memory
302506		square1001	Sorting (IOI15_sorting)	C++14	20 / 100	189 ms	632 KiB

sorting

#include "sorting.h"
#include <random>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
mt19937 mt(2009190008);
int rand_rng(int l, int r) {
	uniform_int_distribution<int> p(l, r - 1);
	return p(mt);
}
int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
	fill(P, P + M, 0);
	fill(Q, Q + M, 0);
	if(is_sorted(S, S + N)) {
		return 0;
	}
	int L = 0;
	while(true) {
		++L;
		vector<bool> vis(N, false);
		int cycles = 0;
		for(int i = 0; i < N; ++i) {
			if(vis[i]) continue;
			int pos = i;
			++cycles;
			while(!vis[pos]) {
				vis[pos] = true;
				pos = S[pos];
			}
		}
		int steps = N - cycles;
		if(L >= steps) break;
	}
	for(int i = 0; i < L; ++i) {
		swap(S[X[i]], S[Y[i]]);
	}
	for(int i = 0; i < L; ++i) {
		int cycles = 0;
		vector<int> col(N, -1);
		for(int j = 0; j < N; ++j) {
			if(col[j] != -1) continue;
			int pos = j;
			while(col[pos] == -1) {
				col[pos] = j;
				pos = S[pos];
			}
			++cycles;
		}
		if(cycles == N) {
			P[i] = 0;
			Q[i] = 0;
		}
		else {
			vector<vector<int> > G(N);
			for(int j = 0; j < N; ++j) {
				G[col[j]].push_back(j);
			}
			for(int j = 0; j < N; ++j) {
				if(G[j].size() >= 2) {
					P[i] = G[j][0];
					Q[i] = G[j][1];
					break;
				}
			}
			swap(S[P[i]], S[Q[i]]);
		}
	}
	for(int i = 0; i < L; ++i) {
		if(P[i] == Q[i]) continue;
		for(int j = L - 1; j >= i + 1; --j) {
			if(X[j] == P[i] && Y[j] != Q[i]) {
				P[i] = Y[j];
			}
			else if(X[j] == Q[i] && Y[j] != P[i]) {
				Q[i] = Y[j];
			}
			else if(Y[j] == P[i] && X[j] != Q[i]) {
				P[i] = X[j];
			}
			else if(Y[j] == Q[i] && X[j] != P[i]) {
				Q[i] = X[j];
			}
		}
	}
	return L;
}

• Subtask 1: 8 / 8
• Subtask 2: 12 / 12
• Subtask 3: 0 / 16
• Subtask 4: 0 / 18
• Subtask 5: 0 / 20
• Subtask 6: 0 / 26