Submission #437670

#	Time	Username	Problem	Language	Result	Execution time	Memory
437670		rainboy	Fountain Parks (IOI21_parks)	C++17	100 / 100	229 ms	19324 KiB

parks

/* https://codeforces.com/blog/entry/92083#comment-807698 (frodakcin) */
#include "parks.h"
#include <string.h>

using namespace std;

typedef vector<int> vi;

const int N = 200000;

unsigned int X = 12345;

int rand_() {
	return (X *= 3) >> 1;
}

int xx[N], yy[N];

void sort(int *ii, int l, int r) {
	while (l < r) {
		int i = l, j = l, k = r, i_ = ii[l + rand_() % (r - l)], tmp;

		while (j < k) {
			int c = xx[ii[j]] != xx[i_] ? xx[ii[j]] - xx[i_] : yy[ii[j]] - yy[i_];

			if (c == 0)
				j++;
			else if (c < 0) {
				tmp = ii[i], ii[i] = ii[j], ii[j] = tmp;
				i++, j++;
			} else {
				k--;
				tmp = ii[j], ii[j] = ii[k], ii[k] = tmp;
			}
		}
		sort(ii, l, i);
		l = k;
	}
}

int ds[N];

int find(int i) {
	return ds[i] < 0 ? i : (ds[i] = find(ds[i]));
}

int join(int i, int j) {
	i = find(i);
	j = find(j);
	if (i == j)
		return 0;
	if (ds[i] > ds[j])
		ds[i] = j;
	else {
		if (ds[i] == ds[j])
			ds[i]--;
		ds[j] = i;
	}
	return 1;
}

int ii[N], jj[N][4];

int construct_roads(vi xx_, vi yy_) {
	int n = xx_.size(), m, i, j, tmp;
	vi uu(n - 1), vv(n - 1), aa(n - 1), bb(n - 1);

	for (i = 0; i < n; i++)
		xx[i] = xx_[i] / 2, yy[i] = yy_[i] / 2, ii[i] = i;
	sort(ii, 0, n);
	for (i = 0; i < n; i++)
		jj[i][0] = jj[i][1] = jj[i][2] = jj[i][3] = -1;
	for (i = 1; i < n; i++)
		if (xx[ii[i - 1]] == xx[ii[i]] && yy[ii[i - 1]] + 1 == yy[ii[i]])
			jj[ii[i - 1]][0] = ii[i], jj[ii[i]][2] = ii[i - 1];
	for (i = 0; i < n; i++)
		tmp = xx[i], xx[i] = yy[i], yy[i] = tmp;
	sort(ii, 0, n);
	for (i = 1; i < n; i++)
		if (xx[ii[i - 1]] == xx[ii[i]] && yy[ii[i - 1]] + 1 == yy[ii[i]])
			jj[ii[i - 1]][1] = ii[i], jj[ii[i]][3] = ii[i - 1];
	for (i = 0; i < n; i++)
		tmp = xx[i], xx[i] = yy[i], yy[i] = tmp;
	memset(ds, -1, n * sizeof *ds);
	m = 0;
	for (i = 0; i < n; i++) {
		if ((j = jj[i][0]) != -1) {
			if ((xx[i] + yy[i]) % 2 == 0) {
				if (join(i, j))
					uu[m] = i, vv[m] = j, aa[m] = xx[i] + xx[j] + 1, bb[m] = yy[i] + yy[j], m++;
			} else {
				if ((jj[i][3] == -1 || jj[j][3] == -1) && join(i, j))
					uu[m] = i, vv[m] = j, aa[m] = xx[i] + xx[j] - 1, bb[m] = yy[i] + yy[j], m++;
			}
		}
		if ((j = jj[i][1]) != -1) {
			if ((xx[i] + yy[i]) % 2 == 0) {
				if (join(i, j))
					uu[m] = i, vv[m] = j, aa[m] = xx[i] + xx[j], bb[m] = yy[i] + yy[j] - 1, m++;
			} else {
				if ((jj[i][0] == -1 || jj[j][0] == -1) && join(i, j))
					uu[m] = i, vv[m] = j, aa[m] = xx[i] + xx[j], bb[m] = yy[i] + yy[j] + 1, m++;
			}
		}
	}
	for (i = 0; i < n; i++)
		if (find(i) != find(0))
			return 0;
	build(uu, vv, aa, bb);
	return 1;
}

• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 20 / 20
• Subtask 5: 20 / 20
• Subtask 6: 30 / 30