Submission #590114

#	Time	Username	Problem	Language	Result	Execution time	Memory
590114		rainboy	Event Hopping (BOI22_events)	C11	100 / 100	150 ms	13012 KiB

events

#include <stdio.h>

#define N	100000
#define L	17	/* L = ceil(log2(N)) */

unsigned int X = 12345;

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

int ll[N], rr[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)
			if (rr[ii[j]] == rr[i_])
				j++;
			else if (rr[ii[j]] < rr[i_]) {
				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 main() {
	static int ii[N], qu[N], pp[L + 1][N];
	int n, q, h, i, i_, j, j_, k, l, cnt, lower, upper;

	scanf("%d%d", &n, &q);
	for (i = 0; i < n; i++) {
		scanf("%d%d", &ll[i], &rr[i]);
		ii[i] = i;
	}
	sort(ii, 0, n);
	cnt = 0;
	for (i = 0, j = 0; j < n; j++) {
		j_ = ii[j];
		while (i < n && rr[i_ = ii[i]] <= rr[j_]) {
			while (cnt && ll[qu[cnt - 1]] >= ll[i_])
				cnt--;
			qu[cnt++] = i_;
			i++;
		}
		lower = -1, upper = cnt;
		while (upper - lower > 1) {
			h = (lower + upper) / 2;
			if (ll[j_] <= rr[qu[h]])
				upper = h;
			else
				lower = h;
		}
		pp[0][j_] = qu[upper];
	}
	for (l = 1; l <= L; l++)
		for (i = 0; i < n; i++)
			pp[l][i] = pp[l - 1][pp[l - 1][i]];
	while (q--) {
		scanf("%d%d", &i, &j), i--, j--;
		if (i == j) {
			printf("0\n");
			continue;
		}
		if (rr[i] > rr[j] || ll[pp[L][j]] > rr[i]) {
			printf("impossible\n");
			continue;
		}
		if (ll[j] <= rr[i]) {
			printf("1\n");
			continue;
		}
		k = 2;
		for (l = L; l >= 0; l--)
			if (ll[pp[l][j]] > rr[i])
				j = pp[l][j], k += 1 << l;
		printf("%d\n", k);
	}
	return 0;
}

Compilation message (stderr)

events.c: In function 'main':
events.c:37:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |  scanf("%d%d", &n, &q);
      |  ^~~~~~~~~~~~~~~~~~~~~
events.c:39:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   39 |   scanf("%d%d", &ll[i], &rr[i]);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
events.c:66:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   66 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

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