可持久化字典树（附BZOJ - 4477 字符串树代码）

Persistent-Trie.cpp

@@ -0,0 +1,137 @@
+#include <cstdio>
+#include <cstring>
+#include <algorithm>
+
+#define NIL 0
+
+using namespace std;
+
+struct node
+{
+	node *next[26];
+	int cnt;
+	node() : cnt(0) { memset(next, 0, sizeof(next)); }
+};
+
+struct vertex
+{
+	int first, depth;
+	node *root;
+}V[100010];
+
+struct edge
+{
+	int endp, next;
+}E[200010];
+
+int n, ec = 2, q, fa[100010][18], k;
+char str[100010][12];
+
+inline void add_edge(int u, int v)
+{
+	E[ec].next = V[u].first;
+	V[u].first = ec;
+	E[ec].endp = v;
+	ec++;
+}
+
+void insert(node *&u, node *old, char *s, int len, int p)
+{
+	u = new node;
+	if (old != NIL) *u = *old;
+	u->cnt++;
+	if (p == len) return;
+	int x = s[p] - 'a';
+	u->next[x] = NIL;
+	insert(u->next[x], old == NIL ? NIL : old->next[x], s, len, p + 1);
+}
+
+int query(node *u, char *s, int len, int p)
+{
+	if (u == NIL) return 0;
+	if (p == len) return u->cnt;
+	int x = s[p] - 'a';
+	return query(u->next[x], s, len, p + 1);
+}
+
+int query(int u, char *s)
+{
+	return query(V[u].root, s, strlen(s), 0);
+}
+
+void dfs(int u, int fa, int depth)
+{
+	::fa[u][0] = fa;
+	V[u].depth = depth;
+	for (int cur = V[u].first; cur != 0; cur = E[cur].next)
+	{
+		if (E[cur].endp != fa)
+		{
+			insert(V[E[cur].endp].root, V[u].root, str[cur >> 1], strlen(str[cur >> 1]), 0);
+			dfs(E[cur].endp, u, depth + 1);
+		}
+	}
+}
+
+void init()
+{
+	V[1].root = new node;
+	dfs(1, 0, 0);
+	for (k = 1; (1 << k) <= n; k++)
+	{
+		for (int i = 1; i <= n; i++)
+		{
+			fa[i][k] = fa[fa[i][k - 1]][k - 1];
+		}
+	}
+	k--;
+}
+
+int lca(int x, int y)
+{
+	if (V[x].depth < V[y].depth)
+	{
+		swap(x, y);
+	}
+	for (int i = k; i >= 0; i--)
+	{
+		if (V[x].depth - (1 << i) >= V[y].depth)
+		{
+			x = fa[x][i];
+		}
+	}
+	if (x == y)
+	{
+		return x;
+	}
+	for (int i = k; i >= 0; i--)
+	{
+		if (fa[x][i] != fa[y][i])
+		{
+			x = fa[x][i];
+			y = fa[y][i];
+		}
+	}
+	return fa[x][0];
+}
+
+int main()
+{
+	scanf("%d", &n);
+	int u, v;
+	for (int i = 1; i < n; i++)
+	{
+		scanf("%d%d%s", &u, &v, str[i]);
+		add_edge(u, v);
+		add_edge(v, u);
+	}
+	init();
+	scanf("%d", &q);
+	char s[12];
+	while (q--)
+	{
+		scanf("%d%d%s", &u, &v, s);
+		printf("%d\n", query(u, s) + query(v, s) - query(lca(u, v), s) * 2);
+	}
+	return 0;
+}