Submission #387248

#	Time	Username	Problem	Language	Result	Execution time	Memory
387248		alireza_kaviani	Sorting (IOI15_sorting)	C++11	100 / 100	929 ms	35808 KiB

sorting

#include <bits/stdc++.h>
#include "sorting.h"
using namespace std;

#define SZ(x)			int((x).size())

const int MAXN = 2e5 + 10;

int A[MAXN] , to[MAXN] , pos[MAXN] , mark[MAXN] , p[MAXN] , q[MAXN];
vector<int> vec , adj[MAXN];

void DFS(int v){
	mark[v] = 1;
	vec.push_back(v);
//	cout << v << endl;
	for(int u : adj[v]){
//		cout << v << ' ' << u << endl;
		if(!mark[u])	DFS(u);
	}
}

int check(int N, int M, int X[], int Y[]) {
//	cout << endl << "==========" << endl << M << endl;
	int cnt = 0;
	fill(p , p + MAXN , 0);
	fill(q , q + MAXN , 0);
	fill(mark , mark + MAXN , 0);
	for(int i = 0 ; i < N ; i++)	adj[i].clear();
	for(int i = 0 ; i < N ; i++)	to[i] = pos[i] = i;
	for(int i = 0 ; i < M ; i++){
		swap(A[X[i]] , A[Y[i]]);
	}
	for(int i = 0 ; i < N ; i++){
//		cout << A[i] << ' ';
		adj[i].push_back(A[i]);
	}
//	cout << endl;
	for(int i = 0 ; i < N ; i++){
		if(!mark[i]){
			vec.clear();
			DFS(i);
//			cout << "DFS " << i << ' ' << SZ(vec) << endl;
//			for(int j : vec)	cout << j << ' ';
			for(int j = 1 ; j < SZ(vec) ; j++){
				if(cnt == M)	return 0;
				p[cnt] = vec[0];
				q[cnt] = vec[j];
//				cout << vec[0] << ' ' << vec[j] << endl;
				cnt++;
			}
//			cout << endl;
		}
	}
	for(int i = M - 1 ; i >= 0 ; i--){
		if(i < cnt){
			p[i] = to[p[i]];
			q[i] = to[q[i]];
		}
		to[pos[X[i]]] = Y[i];
		to[pos[Y[i]]] = X[i];
		swap(pos[X[i]] , pos[Y[i]]);
	}
	return 1;
}

int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]){
	int l = -1 , r = N;
	while(r - l > 1){
		int mid = l + r >> 1;
		for(int i = 0 ; i < N ; i++)	A[i] = S[i];
		if(check(N , mid , X , Y))	r = mid;
		else	l = mid;
	}
	for(int i = 0 ; i < N ; i++)	A[i] = S[i];
	int tmp = check(N , r , X , Y);
	for(int i = 0 ; i < r ; i++){
		P[i] = p[i];
		Q[i] = q[i];
	}
	return r;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:69:15: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   69 |   int mid = l + r >> 1;
      |             ~~^~~
sorting.cpp:75:6: warning: unused variable 'tmp' [-Wunused-variable]
   75 |  int tmp = check(N , r , X , Y);
      |      ^~~
sorting.cpp:66:39: warning: unused parameter 'M' [-Wunused-parameter]
   66 | int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]){
      |                                   ~~~~^

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