Submission #544752

#	Time	Username	Problem	Language	Result	Execution time	Memory
544752		rainboy	Graph (BOI20_graph)	C11	100 / 100	172 ms	26416 KiB

Graph

#include <stdio.h>
#include <stdlib.h>

#define N	100000
#define M	200000

unsigned int X = 12345;

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

int ii[M], jj[M], ww[M];
int *eh[N], eo[N];

void append(int i, int h) {
	int o = eo[i]++;

	if (o >= 2 && (o & o - 1) == 0)
		eh[i] = (int *) realloc(eh[i], o * 2 * sizeof *eh[i]);
	eh[i][o] = h;
}

int ff[N], cc[N], aa[N], bb[N], cnt;

void dfs2(int i, int a);

int dfs1(int f, int i, int c, int a) {
	int o;

	if (cc[i]) {
		if (cc[i] != c) {
			int j;

			j = i ^ ii[f] ^ jj[f], a = 0;
			while (j != i)
				a = ww[ff[j]] - a, j ^= ii[ff[j]] ^ jj[ff[j]];
			a = ww[f] - a, j ^= ii[f] ^ jj[f];
			dfs2(j, a / 2);
			return 1;
		}
		return 0;
	}
	ff[i] = f, cc[i] = c, aa[i] = a;
	bb[cnt++] = c == 1 ? -a : a;
	for (o = eo[i]; o--; ) {
		int h = eh[i][o], j = i ^ ii[h] ^ jj[h];

		if (dfs1(h, j, c ^ 3, ww[h] - a))
			return 1;
	}
	return 0;
}

void dfs2(int i, int a) {
	int o;

	if (cc[i] == -1)
		return;
	cc[i] = -1, aa[i] = a;
	for (o = eo[i]; o--; ) {
		int h = eh[i][o], j = i ^ ii[h] ^ jj[h];

		dfs2(j, ww[h] - a);
	}
}

int median(int *aa, int n) {
	int l = 0, r = n, m = (n - 1) / 2;

	while (1) {
		int i = l, j = l, k = r, a = aa[l + rand_() % (r - l)], tmp;

		while (j < k)
			if (aa[j] == a)
				j++;
			else if (aa[j] < a) {
				tmp = aa[i], aa[i] = aa[j], aa[j] = tmp;
				i++, j++;
			} else {
				k--;
				tmp = aa[j], aa[j] = aa[k], aa[k] = tmp;
			}
		if (m < i)
			r = i;
		else if (m >= k)
			l = k;
		else
			return a;
	}
}

int main() {
	int n, m, h, i, j;

	scanf("%d%d", &n, &m);
	for (i = 0; i < n; i++)
		eh[i] = (int *) malloc(2 * sizeof *eh[i]);
	for (h = 0; h < m; h++) {
		scanf("%d%d%d", &i, &j, &ww[h]), i--, j--, ww[h] *= 2;
		ii[h] = i, jj[h] = j;
		append(i, h), append(j, h);
	}
	for (i = 0; i < n; i++)
		if (!cc[i]) {
			cnt = 0;
			if (!dfs1(-1, i, 1, 0))
				dfs2(i, median(bb, cnt));
		}
	for (h = 0; h < m; h++)
		if (aa[ii[h]] + aa[jj[h]] != ww[h]) {
			printf("NO\n");
			return 0;
		}
	printf("YES\n");
	for (i = 0; i < n; i++)
		if (aa[i] > 0)
			printf("%d.%d ", aa[i] / 2, aa[i] % 2 == 0 ? 0 : 5);
		else if (aa[i] < 0)
			printf("-%d.%d ", -aa[i] / 2, -aa[i] % 2 == 0 ? 0 : 5);
		else
			printf("0.0 ");
	printf("\n");
	return 0;
}

Compilation message (stderr)

Graph.c: In function 'append':
Graph.c:19:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   19 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
Graph.c: In function 'main':
Graph.c:96:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   96 |  scanf("%d%d", &n, &m);
      |  ^~~~~~~~~~~~~~~~~~~~~
Graph.c:100:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  100 |   scanf("%d%d%d", &i, &j, &ww[h]), i--, j--, ww[h] *= 2;
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 12 / 12
• Subtask 3: 17 / 17
• Subtask 4: 24 / 24
• Subtask 5: 42 / 42