Submission #426125

#	Time	Username	Problem	Language	Result	Execution time	Memory
426125		_fractal	Sorting (IOI15_sorting)	C++14	100 / 100	522 ms	28004 KiB

sorting

#include "sorting.h"
#include <iostream>
#include <algorithm>
#include <stack>
using namespace std;
 

int findSwapPairs(int N, int SS[], int M, int X[], int Y[], int P[], int Q[]) {
	int A[N], pos[N], sop[N], L[M], R[M], ret = (1<<30), S[N];
	int tl = 0, tr = M - 1;
	while (tl <= tr) {
		int m = tl + tr >> 1;
		for (int i = 0; i < N; ++i)
			A[i] = i, S[i] = SS[i];
		for (int i = m; i >= 0; --i)
			swap(A[X[i]], A[Y[i]]);
		int bad = 0;
		for (int i = 0; i < N; ++i)
			if (S[i] != i)
				bad++;
		int r = -1;
		stack<int>s;
		for (int j = 0; j < N; ++j)
			pos[A[j]] = j, sop[S[j]] = j, s.push(j);
		for (int i = 0; i <= m; ++i) {
			P[i] = Q[i] = 0;
			if (bad == 0) {
				r = i;
				break;
			}
			if (S[X[i]] != X[i])
				bad--;
			if (S[Y[i]] != Y[i])
				bad--;
			swap(S[X[i]], S[Y[i]]);
			swap(pos[A[X[i]]], pos[A[Y[i]]]);
			swap(sop[S[X[i]]], sop[S[Y[i]]]);
			swap(A[X[i]], A[Y[i]]);
			if (S[X[i]] != X[i])
				bad++;
			if (S[Y[i]] != Y[i])
				bad++;
			if (bad == 0) {
				r = i + 1;
				break;
			}
			while (s.size() && sop[s.top()] == pos[s.top()])
				s.pop();
			if (s.size()) {
				Q[i] = sop[s.top()];
				P[i] = pos[s.top()];
				s.pop();
			}
			if (S[Q[i]] != Q[i])
				bad--;
			if (S[P[i]] != P[i])
				bad--;
			swap(S[Q[i]], S[P[i]]);
			swap(sop[S[Q[i]]], sop[S[P[i]]]);
			if (S[Q[i]] != Q[i])
				bad++;
			if (S[P[i]] != P[i])
				bad++;
		}
		if (bad) {
			tl = m + 1;
			continue;
		}
		tr = m - 1;
		if (r == -1) r = m + 1;
		if (ret >= r) {
			ret = r;
			for (int i = 0; i < r; ++i)
				L[i] = Q[i], R[i] = P[i];
		}
	}
	for (int i = 0; i < ret; ++i)
		Q[i] = L[i], P[i]= R[i];
	return ret;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:12:14: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   12 |   int m = tl + tr >> 1;
      |           ~~~^~~~

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