Submission #66427

#	Time	Username	Problem	Language	Result	Execution time	Memory
66427		Hoget157	Sorting (IOI15_sorting)	C++14	100 / 100	270 ms	12636 KiB

sorting

#include <bits/stdc++.h>
#define pb push_back
using namespace std;

int n,*a,m,*x,*y,r;

bool C(int k){
	int p[200000],ans = 0;
	bool used[200000] = {};
	for(int i = 0;i < n;i++) p[i] = a[i];
	for(int i = 0;i < k;i++) swap(p[x[i]],p[y[i]]);
	for(int i = 0;i < n;i++){
		if(!used[i]){
			int pos = i;
			while(!used[pos]){
				ans++;
				used[pos] = true;
				pos = p[pos];
			}
			ans--;
		}
	}
	return ans <= k;
}

typedef pair<int,int> pii;

int b[200000];

int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
    n = N;a = S;m = M;x = X;y = Y;
	int low = -1,up = m;
	while(up - low > 1){
		int mid = (up + low) / 2;
		if(C(mid)) up = mid;
		else low = mid;
	}
	r = up;
	vector<pii> vec;
	int p[200000];
	bool used[200000] = {};
	for(int i = 0;i < n;i++) p[i] = a[i];
	for(int i = 0;i < r;i++) swap(p[x[i]],p[y[i]]);
	for(int i = 0;i < n;i++) b[p[i]] = i;
	for(int i = 0;i < n;i++){
		if(b[i] != i){
			int c = i,d = b[i];
			vec.pb(pii(p[c],p[d]));
			swap(p[c],p[d]);
			swap(b[p[c]],b[p[d]]);
		}
	}
	for(int i = 0;i < n;i++) b[S[i]] = i;
	for(int i = 0;i < r;i++){
		swap(S[x[i]],S[y[i]]);
		swap(b[S[x[i]]],b[S[y[i]]]);
		if(i < vec.size()){
			P[i] = b[vec[i].first];
			Q[i] = b[vec[i].second];
			swap(S[P[i]],S[Q[i]]);
			swap(b[S[P[i]]],b[S[Q[i]]]);
		}else{
			P[i] = 0;
			Q[i] = 0;
		}
	}
	return r;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:57:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(i < vec.size()){
      ~~^~~~~~~~~~~~
sorting.cpp:41:7: warning: unused variable 'used' [-Wunused-variable]
  bool used[200000] = {};
       ^~~~

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