Submission #302723

#	Time	Username	Problem	Language	Result	Execution time	Memory
302723		square1001	Sorting (IOI15_sorting)	C++14	0 / 100	4 ms	512 KiB

sorting

#include "sorting.h"
#include <random>
#include <vector>
#include <cassert>
#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 pl = 0, pr = M;
	while(pr - pl > 1) {
		int pm = (pl + pr) >> 1;
		vector<int> T(S, S + N);
		for(int i = 0; i < pm; ++i) {
			swap(T[X[i]], T[Y[i]]);
		}
		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 = T[pos];
			}
		}
		int steps = N - cycles;
		if(pm >= steps) pr = pm;
		else pl = pm;
	}
	int L = pr;
	for(int i = 0; i < L; ++i) {
		swap(S[X[i]], S[Y[i]]);
	}
	vector<bool> vis2(N, false);
	int cl = 0;
	for(int i = 0; i < N; ++i) {
		if(vis2[i]) continue;
		vector<int> path;
		int pos = i;
		while(!vis2[pos]) {
			path.push_back(pos);
			vis2[pos] = true;
			pos = S[pos];
		}
		for(int j = int(path.size()) - 1; j >= 1; --j) {
			P[cl] = path[j - 1];
			Q[cl] = path[j];
			++cl;
		}
	}
	for(int i = 0; i < L; ++i) {
		if(P[i] == Q[i]) continue;
		int pv = P[i], qv = Q[i];
		for(int j = L - 1; j >= i + 1; --j) {
			if(pv == X[j]) pv = Y[j];
			else if(pv == Y[j]) pv = X[j];
			if(qv == X[j]) qv = Y[j];
			else if(qv = Y[j]) qv = X[j];
		}
		P[i] = pv;
		Q[i] = qv;
	}
	return L;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:69:15: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   69 |    else if(qv = Y[j]) qv = X[j];
      |            ~~~^~~~~~

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