可持久化数组

Persistent-Array.cpp

@@ -0,0 +1,123 @@
+#include <cstdio>
+
+#define NIL 0
+#define ELEMENT_COUNT 100000
+#define EDITION_COUNT 100000
+#define POOL_SIZE 1000000
+
+using namespace std;
+
+struct node
+{
+	node *lch, *rch;
+	int v;
+	node(int _v = 0) : v(_v) { lch = rch = NIL; }
+	void* operator new (size_t);
+}*root[EDITION_COUNT], pool[POOL_SIZE];
+int top = 0;
+
+int n, d[ELEMENT_COUNT], cur = 0, used = 1;
+
+void* node::operator new (size_t)
+{
+	return pool + top++;
+}
+
+void build(node *&u, int l, int r)
+{
+	u = new node;
+	if (l == r)
+	{
+		u->v = d[l];
+	}
+	else
+	{
+		int mid = (l + r) >> 1;
+		build(u->lch, l, mid);
+		build(u->rch, mid + 1, r);
+	}
+}
+
+void modify(node *&u, node *old, int l, int r, int k, int v)
+{
+	u = new node;
+	if (l == r)
+	{
+		u->v = v;
+	}
+	else
+	{
+		int mid = (l + r) >> 1;
+		if (k <= mid)
+		{
+			u->rch = old->rch;
+			modify(u->lch, old->lch, l, mid, k, v);
+		}
+		else
+		{
+			u->lch = old->lch;
+			modify(u->rch, old->rch, mid + 1, r, k, v);
+		}
+	}
+}
+
+int query(node *u, int l, int r, int k)
+{
+	if (l == r)
+	{
+		return u->v;
+	}
+	else
+	{
+		int mid = (l + r) >> 1;
+		if (k <= mid)
+		{
+			return query(u->lch, l, mid, k);
+		}
+		else
+		{
+			return query(u->rch, mid + 1, r, k);
+		}
+	}
+}
+
+int main()
+{
+	int op, e, k, x;
+	scanf("%d", &n);
+	for (int i = 1; i <= n; i++)
+	{
+		scanf("%d", &d[i]);
+	}
+	build(root[cur], 1, n);
+	while (true)
+	{
+		scanf("%d", &op);
+		if (op == 1)
+		{
+			scanf("%d%d", &k, &x);
+			modify(root[used], root[cur], 1, n, k, x);
+			cur = used;
+			used++;
+		}
+		else if (op == 2)
+		{
+			scanf("%d%d", &e, &k);
+			printf("%d\n", query(root[e], 1, n, k));
+		}
+		else if (op == 3)
+		{
+			scanf("%d", &e);
+			cur = e;
+		}
+		else if (op == 0)
+		{
+			break;
+		}
+		else
+		{
+			printf("No such command!\n");
+		}
+	}
+	return 0;
+}