Submission #124566

#	Time	Username	Problem	Language	Result	Execution time	Memory
124566		RockyB	Sorting (IOI15_sorting)	C++14	74 / 100	194 ms	16368 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)5e5 + 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 pos[n];
	rep(i, 0, n) {
		pos[b[i]] = i;
	}
	int cnt = 0;
	rep(i, 0, n) {
		if (b[i] != i) {
			swap(b[i], b[pos[i]]);
			swap(pos[b[i]], pos[b[pos[i]]]);
			++cnt;
		}
	}
	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];
		}
	} 
	if (!m) assert(0);
	// copying
	
	int l = 0, r = m, res = -1;	
	while (l <= r) {
		int mid = (l + r) >> 1;
		if (check(mid)) res = mid, r = mid - 1;
		else l = mid + 1;
	}
	//if (res == -1) ioi
	// opt len found

	rep(i, 0, res) {
		P[i] = Q[i] = 0;
	}
	rep(i, 0, n) {
		b[i] = a[i];
	}
	rep(i, 0, res) {
		swap(b[x[i]], b[y[i]]);
	}
	vector <int> st;
	int go[n], pos[n], fnd[n];
	rep(i, 0, n) {
		go[b[i]] = i;
		pos[i] = b[i];
	}
	rep(i, 0, n) {
		if (go[i] != i) st.pb(i);
	}
	int ptr = 0;
	if (!sz(st)) {
		ptr = 0;
		P[ptr] = 0;
		Q[ptr] = 0;
		return res;
	}
	swap(a[X[ptr]], a[Y[ptr]]);
	rep(i, 0, n) {
		fnd[a[i]] = i;
	}

	for (auto x : st) {
		if (go[x] == x) {
			continue;
		}
		/* rep(i, 0, n) {
			cerr << a[i] << ' ';
		}
		cerr << nl;
		rep(i, 0, n) {
			cerr << go[i] << ' ';
		}
		cerr << nl; */

		int p1 = fnd[x];

		//cerr << a[p1] << ' ' << x << nl;


		rep(i, 0, n) {
			i = pos[x];
			if (go[i] == x) {
				int p2 = fnd[i];
				//cerr << a[p2] << ' ' << i << nl;
				P[ptr] = p1;
				Q[ptr] = p2;
				swap(go[x], go[i]);
				swap(pos[go[x]], pos[go[i]]);
				swap(fnd[x], fnd[i]);
				swap(a[p1], a[p2]);
				ptr++;
				break;
			}
			break;
		}

		/*		
		cerr << " -> " << x << nl;
		rep(i, 0, n) cerr << a[i] << ' ';
		cerr << nl;
		rep(i, 0, n) cerr << go[i] << ' ';
		cerr << nl << nl;*/
		
		if (ptr < m) {
			swap(a[X[ptr]], a[Y[ptr]]);
			swap(fnd[a[X[ptr]]], fnd[a[Y[ptr]]]);
			///// don't use/// swap(go[a[X[ptr]]], go[a[Y[ptr]]]);
		}
	}

	
	return res;
}

#ifdef IOI2018

namespace gen {


	void gen() {
		int N, M;
		N = rand() % 5 + 1;
		int *S = (int*)malloc(sizeof(int) * (unsigned int)N);
		for (int i = 0; i < N; ++i)
			S[i] = i;
		random_shuffle(S, S + N);

		printf ("%d\n", N);
		fflush(stdout);
		int A[N];
		for (int i = 0; i < N; i++) {
				A[i] = S[i];
				printf ("%d ", A[i]);
		}
		printf ("\n");
		fflush(stdout);

		M = rand() % 5 + 1;
		printf ("%d\n", M);
		fflush(stdout);
		int *X = (int*)malloc(sizeof(int) * (unsigned int)M), *Y = (int*)malloc(sizeof(int) * (unsigned int)M);
		for (int i = 0; i < M; ++i) {
				X[i] = rand() % N;
				Y[i] = rand() % N;
				printf ("%d %d\n", X[i], Y[i]);
				fflush(stdout);
		}
		int *P = (int*)malloc(sizeof(int) * (unsigned int)M), *Q = (int*)malloc(sizeof(int) * (unsigned int)M);
		int ans = findSwapPairs(N, S, M, X, Y, P, Q);
		printf("%d\n", ans);
		fflush(stdout);

		//assert(ans <= 30 * N);
		for (int i = 0; i < ans; ++i) {
					if (i < M) swap(A[X[i]], A[Y[i]]);
					swap(A[P[i]], A[Q[i]]);
			}
			for (int i = 0; i < N; i++) {
				//assert(A[i] == i);
					printf("%d ", A[i]);
			}
			for (int i = 0; i < N; i++) {
					assert(A[i] == i);
					//printf("%d ", A[i]);
			}
	}

}

int main() {
	rep(i, 1, 1000) {
		printf ("Case: %d\n", i);
		fflush(stdout);
		srand(i);
		gen :: gen();
		printf ("\n");
		fflush(stdout);
	}
}

#endif

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:108:12: warning: declaration of 'x' shadows a global declaration [-Wshadow]
  for (auto x : st) {
            ^
sorting.cpp:30:23: note: shadowed declaration is here
 int a[MAXN], b[MAXN], x[MAXN], y[MAXN];
                       ^

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