結果

問題 No.3113 The farthest point
ユーザー pengin_2000
提出日時 2025-04-18 23:33:46
言語 C
(gcc 13.3.0)
結果
AC  
実行時間 711 ms / 2,000 ms
コード長 4,205 bytes
コンパイル時間 307 ms
コンパイル使用メモリ 29,584 KB
実行使用メモリ 28,156 KB
最終ジャッジ日時 2025-04-18 23:33:59
合計ジャッジ時間 11,198 ms
ジャッジサーバーID
（参考情報） 		judge2 / judge1
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 33
権限があれば一括ダウンロードができます
コンパイルメッセージ
main.c: In function ‘main’:
main.c:81:9: warning: ignoring return value of ‘scanf’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   81 |         scanf("%lld", &n);
      |         ^~~~~~~~~~~~~~~~~
main.c:86:17: warning: ignoring return value of ‘scanf’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   86 |                 scanf("%lld %lld %lld", &u[i], &v[i], &w[i]);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

ソースコード

diff # 

#include<stdio.h>
long long int u[400005], v[400005], w[400005];
long long int h[400005], l, z;
long long int depth[200005], par[200005], pw[200005];
long long int comp_h(long long int a, long long int b)
{
	if (z == 0)
	{
		if (u[h[a]] > u[h[b]])
			return 1;
		else if (u[h[a]] < u[h[b]])
			return -1;
		else if (v[h[a]] == par[u[h[a]]])
			return 1;
		else
			return -1;
	}
	else
	{
		if (depth[h[a]] < depth[h[b]])
			return 1;
		else
			return -1;
	}
}
void swap_h(long long int a, long long int b)
{
	long long int f = h[a];
	h[a] = h[b];
	h[b] = f;
	return;
}
void push(long long int ne)
{
	h[l] = ne;
	long long int p = l++;
	for (; p > 0; p = (p - 1) / 2)
		if (comp_h((p - 1) / 2, p) > 0)
			swap_h((p - 1) / 2, p);
	return;
}
long long int pop()
{
	swap_h(0, --l);
	long long int p = 0;
	for (;;)
	{
		if (2 * p + 2 < l)
		{
			if (comp_h(2 * p + 1, 2 * p + 2) > 0)
			{
				if (comp_h(p, 2 * p + 2) > 0)
					swap_h(p, 2 * p + 2);
				p = 2 * p + 2;
			}
			else
			{
				if (comp_h(p, 2 * p + 1) > 0)
					swap_h(p, 2 * p + 1);
				p = 2 * p + 1;
			}
		}
		else if (2 * p + 1 < l)
		{
			if (comp_h(p, 2 * p + 1) > 0)
				swap_h(p, 2 * p + 1);
			p = 2 * p + 1;
		}
		else
			break;
	}
	return h[l];
}
long long int c[400005];
long long int dp[200005];
long long int max_id[200005][2];
long long int next_id[200005];
int main()
{
	long long int n;
	scanf("%lld", &n);
	long long int m = n - 1;;
	long long int i, j;
	for (i = 0; i < m; i++)
	{
		scanf("%lld %lld %lld", &u[i], &v[i], &w[i]);
		u[i + m] = --v[i];
		v[i + m] = --u[i];
		w[i + m] = w[i];
	}
	m *= 2;
	z = 0;
	l = 0;
	for (i = 0; i < m; i++)
		push(i);
	for (i = 0; i < m; i++)
		c[i] = pop();
	c[m] = m;
	u[m] = n + 1;
	int min, mid, max;
	for (i = 0; i < n; i++)
		depth[i] = -1;
	depth[0] = 0;
	h[0] = 0;
	l = 1;
	while (l > 0)
	{
		l--;
		i = h[l];
		min = -1;
		max = m;
		while (max - min > 1)
		{
			mid = (max + min) / 2;
			if (u[c[mid]] < i)
				min = mid;
			else
				max = mid;
		}
		for (; u[c[max]] == i; max++)
		{
			if (depth[v[c[max]]] < 0)
			{
				depth[v[c[max]]] = depth[i] + 1;
				par[v[c[max]]] = i;
				pw[v[c[max]]] = w[c[max]];
				h[l] = v[c[max]];
				l++;
			}
		}
	}
	par[0] = 0;
	pw[0] = 0;
	l = 0;
	z = 0;
	for (i = 0; i < m; i++)
		push(i);
	for (i = 0; i < m; i++)
		c[i] = pop();
	for (i = 0; i < n; i++)
	{
		dp[i] = 0;
		max_id[i][0] = max_id[i][1] = -1;
	}
	z = 1;
	l = 0;
	for (i = 1; i < n; i++)
		push(i);
	while (l > 0)
	{
		i = pop();
		if (dp[par[i]] < dp[i] + pw[i])
			dp[par[i]] = dp[i] + pw[i];
	}
	for (j = 0; u[c[j]] == 0; j++)
	{
		i = v[c[j]];
		if (max_id[0][0] < 0)
			max_id[0][0] = i;
		else if (dp[i] + pw[i] > dp[max_id[0][0]] + pw[max_id[0][0]])
		{
			max_id[0][1] = max_id[0][0];
			max_id[0][0] = i;
		}
		else if (dp[i] + pw[i] > dp[max_id[0][1]] + pw[max_id[0][1]])
			max_id[0][1] = i;
	}
	next_id[0] = 0;
	for (i = 1; i < n; i++)
		for (next_id[i] = next_id[i - 1]; u[c[next_id[i]]] < i; next_id[i]++);
	long long int now_root = 0, next_root;
	long long int ans = dp[0];
	for (;;)
	{
		if (now_root != u[c[next_id[now_root]]])
			break;
		next_root = v[c[next_id[now_root]]];
		next_id[now_root]++;
		if (max_id[now_root][0] == next_root)
		{
			dp[now_root] = dp[max_id[now_root][1]] + pw[max_id[now_root][1]];
			if (dp[now_root] < 0)
				dp[now_root] = 0;
		}
		par[now_root] = next_root;
		pw[now_root] = pw[next_root];
		now_root = next_root;
		if (max_id[now_root][0] < 0)
		{
			min = -1;
			max = m;
			while (max - min > 1)
			{
				mid = (max + min) / 2;
				if (u[c[mid]] < now_root)
					min = mid;
				else
					max = mid;
			}
			for (; u[c[max]] == now_root; max++)
			{
				i = v[c[max]];
				if (max_id[now_root][0] < 0)
					max_id[now_root][0] = i;
				else if (dp[i] + pw[i] > dp[max_id[now_root][0]] + pw[max_id[now_root][0]])
				{
					max_id[now_root][1] = max_id[now_root][0];
					max_id[now_root][0] = i;
				}
				else if (dp[i] + pw[i] > dp[max_id[now_root][1]] + pw[max_id[now_root][1]])
					max_id[now_root][1] = i;
			}
		}
		dp[now_root] = dp[max_id[now_root][0]] + pw[max_id[now_root][0]];
		if (dp[now_root] < 0)
			dp[now_root] = 0;
		if (ans < dp[now_root])
			ans = dp[now_root];
	}
	printf("%lld\n", ans);
	return 0;
}
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