Submission #124430

#	Time	Username	Problem	Language	Result	Execution time	Memory
124430		RockyB	Sorting (IOI15_sorting)	C++17	0 / 100	4 ms	632 KiB

sorting

/// In The Name Of God

#include "sorting.h"
#include <bits/stdc++.h>

#define f first
#define s second

#define pb push_back
#define pp pop_back
#define mp make_pair

#define sz(x) (int)x.size()
#define sqr(x) ((x) * 1ll * (x))
#define all(x) x.begin(), x.end()

#define rep(i, l, r) for (int i = (l); i < (r); i++)
#define per(i, l, r) for (int i = (l); i >= (r); i--)

#define Kazakhstan ios_base :: sync_with_stdio(0), cin.tie(0), cout.tie(0);

#define nl '\n'
#define ioi exit(0);

const int MAXN = (int)2e5 + 7;

using namespace std;

int n, m;
int a[MAXN], b[MAXN], x[MAXN], y[MAXN];

bool check(int len) {
	rep(i, 0, n) {
		b[i] = a[i];
	}
	rep(i, 0, len) {
		swap(b[x[i]], b[y[i]]);
	}
	int cnt = 0;
	rep(i, 0, n) {
		if (b[i] != i) {
			++cnt;
			swap(b[i], b[b[i]]);
		}
	}
	if (cnt > len) return 0;
	return 1;
}
int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
	{
		n = N;
		m = M;
		rep(i, 0, n) {
			a[i] = S[i];
		}
		rep(i, 0, m) {
			x[i] = X[i];
			y[i] = Y[i];
		}
	} // copying

	int l = 1, r = M, res = -1;	
	while (l <= r) {
		int mid = (l + r) >> 1;
		if (check(mid)) res = mid, r = mid - 1;
		else l = mid + 1;
	}
	assert(res != -1);
	rep(i, 0, n) {
		b[i] = a[i];
	}
	rep(i, 0, res) {
		swap(b[x[i]], b[y[i]]);
	}
	vector < pair <int, int> > need;
	rep(i, 0, n) {
		if (b[i] != i) {
			need.pb({b[i], b[b[i]]});
			swap(b[i], b[b[i]]);
		}
	}
	rep(i, 0, res) {
		if (!sz(need)) {
			swap(S[X[i]], S[Y[i]]);
			P[i] = 0;
			Q[i] = 0;
		}
		else {
			int v1 = need.back().f, v2 = need.back().s;
			need.pop_back();
			swap(S[X[i]], S[Y[i]]);
			int p1 = -1, p2;
			rep(j, 0, n) {
				if (S[j] == v1 || S[j] == v2) {
					if (p1 == -1) p1 = j;
					p2 = j;
				}
			}
			P[i] = p1;
			Q[i] = p2;
			swap(S[p1], S[p2]);
		}
	}
	return res;
}

#ifdef IOI2018

int main() {
	if (0) {
		freopen ("sorting.in", "r", stdin);
		int n, m;
		cin >> n;
		int s[n], c[n];
		for (int i = 0; i < n; i++) cin >> s[i], c[i] = s[i];
		cin >> m;
		int x[m], y[m];
		for (int i = 0; i < m; i++) cin >> x[i] >> y[i];
		int p[m], q[m];
		int ans = findSwapPairs(n, s, m, x, y, p, q);
		for (int i = 0; i < ans; i++) {
			swap(c[x[i]], c[y[i]]);
			swap(c[p[i]], c[q[i]]);
		}

		for (int i = 0; i < n; i++) {
			cout << c[i] << ' ';
		}

		ioi
	}


	srand(time(0));
	for (int T = 5; T <= 100; T++) {

		srand(T);

		int n = rand() % 5 + 1, m = 30 * n;
		int s[n], a[n], c[n];
		for (int i = 0; i < n; i++) s[i] = i;
		random_shuffle(s, s + n);
		for (int i = 0; i < n; i++) a[i] = c[i] = s[i];
		int x[m], y[m];
		for (int i = 0; i < m; i++) {
			x[i] = 0, y[i] = 1;
		}

		int p[m], q[m];

		int ans = findSwapPairs(n, s, m, x, y, p, q);

		for (int i = 0; i < ans; i++) {
			swap(c[x[i]], c[y[i]]);
			swap(c[p[i]], c[q[i]]);
		}

		bool bad = 0;
		for (int i = 0; i < n; i++) {
			if (c[i] != i) bad = 1;
		}


		if (bad == 1) {	
			cout << n << nl;
			for (int i = 0; i < n; i++) cout << a[i] << ' ';
			cout << nl;
			cout << m << nl;
			for (int i = 0; i < m; i++) {
				cout << x[i] << ' ' << y[i] << nl;
			}

			ioi
			assert(0);	
		}
	}
}

#endif

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:100:9: warning: 'p2' may be used uninitialized in this function [-Wmaybe-uninitialized]
    Q[i] = p2;
    ~~~~~^~~~

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