Submission #170901

#	Time	Username	Problem	Language	Result	Execution time	Memory
170901		socho	Sorting (IOI15_sorting)	C++14	0 / 100	3 ms	760 KiB

sorting

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

const int MXN = 200005;
int n, m;
int seq[MXN];
pair<int, int> plan[MXN];
vector<pair<int, int> > ans;

bool works(int sw) {
	// cout << "try: " << sw << ' ';
	ans.clear();
	int nsw[n];
	for (int i=0; i<n; i++) nsw[i] = seq[i];
	int where[n];
	for (int i=0; i<sw; i++) {
		int a = plan[i].first, b = plan[i].second;
		swap(nsw[a], nsw[b]);
	}
	for (int i=0; i<n; i++) {
		where[nsw[i]] = i;
	}
	int need = 0;
	for (int i=0; i<n; i++) {
		if (nsw[i] == i) continue;
		need++;
		int ati = nsw[i];
		int whei = where[i];
		where[ati] = whei;
		where[i] = i;
		nsw[i] = i;
		nsw[ati] = whei;
		ans.push_back(make_pair(i, whei));
	}
	// cout << (need <= sw) << endl;
	// if (sw == 3) return true;
	return need <= sw;
}

int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {

    
    n = N;
    m = M;
    for (int i=0; i<n; i++) seq[i] = S[i];
    for (int i=0; i<m; i++) {
		plan[i].first = X[i];
		plan[i].second = Y[i];
	}
    
    int low = 0;
    int high = M + 1;
    
    while (low + 1 < high) {
		int mid = (low + high) / 2;
		if (works(mid)) {
			high = mid;
		}
		else {
			low = mid;
		}
	}
	if (works(low)) {
		works(low);
		for (int i=0; i<low; i++) {
			P[i] = ans[i].first;
			Q[i] = ans[i].second;
		}
		return low;
	}
	else {
		works(high);
		for (int i=0; i<high; i++) {
			P[i] = ans[i].first;
			Q[i] = ans[i].second;
		}
		return high;
	}
    
}

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