Submission #1072304

#	Time	Username	Problem	Language	Result	Execution time	Memory
1072304		rainboy	Summer Driving (CCO24_day1problem3)	C11	9 / 25	6074 ms	52820 KiB

Main

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

#define N	300000
#define INF	0x3f3f3f3f

int min(int a, int b) { return a < b ? a : b; }
int max(int a, int b) { return a > b ? a : b; }

int n, r, a, b;
int *ej[N], eo[N];

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

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

int ii[N], dd[N], pp[N], pp_[N], ll[N], ta[N], tb[N], qu[N];

void dfs(int i) {
	static int t_;
	static int stack[N];
	int o;

	qu[ta[i] = t_++] = i;
	stack[dd[i]] = i;
	pp_[i] = dd[i] < a - 1 ? -1 : stack[dd[i] - a + 1];
	ll[i] = 0;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != pp[i]) {
			dfs(j);
			ll[i] = max(ll[i], ll[j] + 1);
		}
	}
	tb[i] = t_;
}

char dp[N], dq[N];

void mark(int l, int r, int d) {
	int i, a;

	for (a = l; a <= r; a++) {
		i = qu[a];
		if (dd[i] <= d && dq[i])
			dq[i] = 0;
	}
}

int solve(int k) {
	static char dq_[N];
	static int dd1[N], dd2[N];
	int h, h_, i, j, j_, j1, j2, o, bad;

	for (h = n - 1; h >= 0; h--) {
		i = ii[h];
		dd1[i] = i < k ? 0 : INF;
		for (o = eo[i]; o--; ) {
			j = ej[i][o];
			if (j != pp[i])
				dd1[i] = min(dd1[i], dd1[j] + 1);
		}
	}
	memset(dq, 1, n * sizeof *dq), memset(dq_, 0, n * sizeof *dq_);
	for (h = n - 1, h_ = n - 1; h >= 0; h--) {
		i = ii[h];
		while (h_ >= 0 && dd[j = ii[h_]] - dd[i] >= a) {
			if (dq[j] && pp_[j] != -1)
				dq_[pp_[j]] = 1;
			h_--;
		}
		if (ll[i] < a) {
			if (dd1[i] > b)
				dp[i] = 1;
			else {
				dp[i] = 0;
				j_ = i >= k ? -1 : -2;
				for (o = eo[i]; o--; ) {
					j = ej[i][o];
					if (j != pp[i] && dd1[j] < b)
						j_ = j_ == -1 ? j : -2;
				}
				if (j_ == -2)
					mark(ta[i], tb[i] - 1, dd[i] + b);
				else
					mark(ta[i], ta[j_] - 1, dd[i] + b), mark(tb[j_], tb[i] - 1, dd[i] + b);
			}
		} else {
			j_ = -1;
			for (o = eo[i]; o--; ) {
				j = ej[i][o];
				if (j != pp[i] && dq_[j])
					j_ = j_ == -1 ? j : -2;
			}
			if (j_ != -1)
				dp[i] = 1;
			else {
				dp[i] = 0;
				j_ = -2;
				for (o = eo[i]; o--; ) {
					j = ej[i][o];
					if (j != pp[i] && ll[j] >= a - 1) {
						j_ = j;
						break;
					}
				}
				mark(ta[i], ta[j_] - 1, dd[i] + b), mark(tb[j_], tb[i] - 1, dd[i] + b);
			}
			if (j_ != -2) {
				bad = i < k;
				for (o = eo[i]; o--; ) {
					j = ej[i][o];
					if (j != pp[i] && j != j_ && (ll[j] >= a - 1 || dd1[j] < b)) {
						bad = 1;
						break;
					}
				}
				if (bad)
					mark(ta[j_], tb[j_] - 1, dd[i] + b);
			}
		}
		j1 = j2 = -1;
		for (o = eo[i]; o--; ) {
			j = ej[i][o];
			if (j != pp[i]) {
				if (j1 == -1 || dd2[j1] > dd2[j])
					j2 = j1, j1 = j;
				else if (j2 == -1 || dd2[j2] > dd2[j])
					j2 = j;
			}
		}
		dd2[i] = !dp[i] ? 0 : (j1 == -1 || dd2[j1] == INF ? INF : dd2[j1] + 1);
		if (j1 != -1)
			mark(ta[i], ta[i], dd[i] + b - (dd2[j1] + 1));
		for (o = eo[i]; o--; ) {
			j = ej[i][o], j_ = j != j1 ? j1 : j2;
			if (j != pp[i] && j_ != -1)
				mark(ta[j], tb[j] - 1, dd[i] + b - (dd2[j_] + 1));
		}
	}
	return dp[r];
}

int main() {
	int cnt, h, i, j, o, k, lower, upper;

	scanf("%d%d%d%d", &n, &r, &a, &b), r--;
	if (a <= b) {
		printf("1\n");
		return 0;
	}
	for (i = 0; i < n; i++)
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
	for (h = 0; h < n - 1; h++) {
		scanf("%d%d", &i, &j), i--, j--;
		append(i, j), append(j, i);
	}
	cnt = 0;
	dd[r] = 0, pp[r] = -1, ii[cnt++] = r;
	for (h = 0; h < cnt; h++) {
		i = ii[h];
		for (o = eo[i]; o--; ) {
			j = ej[i][o];
			if (j != pp[i])
				dd[j] = dd[i] + 1, pp[j] = i, ii[cnt++] = j;
		}
	}
	dfs(r);
	lower = 0, upper = n;
	while (upper - lower > 1) {
		k = (lower + upper) / 2;
		if (solve(k))
			lower = k;
		else
			upper = k;
	}
	printf("%d\n", upper);
	return 0;
}

Compilation message (stderr)

Main.c: In function 'append':
Main.c:17:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   17 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
Main.c: In function 'main':
Main.c:153:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  153 |  scanf("%d%d%d%d", &n, &r, &a, &b), r--;
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Main.c:161:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  161 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 1 / 1
• Subtask 2: 0 / 4
• Subtask 3: 5 / 5
• Subtask 4: 3 / 3
• Subtask 5: 0 / 4
• Subtask 6: 0 / 6
• Subtask 7: 0 / 2