From f41d01589c5da454cb271c6920fc66dd563c644e Mon Sep 17 00:00:00 2001
From: Wei Yang <richard.weiyang@gmail.com>
Date: Mon, 12 Nov 2018 10:08:38 +0800
Subject: [PATCH] binary tree in array

---
 c-cpp/23_binarytree/binarytree.c | 83 ++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 c-cpp/23_binarytree/binarytree.c

diff --git a/c-cpp/23_binarytree/binarytree.c b/c-cpp/23_binarytree/binarytree.c
new file mode 100644
index 00000000..4143cd17
--- /dev/null
+++ b/c-cpp/23_binarytree/binarytree.c
@@ -0,0 +1,83 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <time.h>
+
+/* Implement binary tree in array */
+
+#define MAX_TREE_NODES (1 << 8)
+
+struct node {
+	int data;
+};
+
+struct binary_tree {
+	union {
+		unsigned long nodes;
+		struct node *n[MAX_TREE_NODES];
+	};
+};
+
+void init_binary_tree(struct binary_tree *tree)
+{
+	int i;
+
+	for(i = 0; i < MAX_TREE_NODES; i++) {
+		tree->n[i] = NULL;
+	}
+}
+
+struct node* create_node(int data)
+{
+	struct node* n;
+
+	n = malloc(sizeof(struct node));
+
+	if (n)
+		n->data = data;
+
+	return n;
+}
+
+void fake_a_tree(struct binary_tree* tree)
+{
+	/* data is in ordered */
+	int i, data[10] = {7, 4, 9, 2, 6, 8, 10, 1, 3, 5};
+
+	init_binary_tree(tree);
+
+	/* root start at 1 */
+	for (i = 0; i < 10; i++)
+		tree->n[i+1] = create_node(data[i]);
+
+	tree->nodes = 10;
+}
+
+void _in_order(struct binary_tree* tree, int index)
+{
+	if (!tree->n[index])
+		return;
+
+	/* left child at (index << 1) */
+	_in_order(tree, index << 1);
+
+	printf("[%2d]: %4d\n", index, tree->n[index]->data);
+
+	/* right child at (index << 1) + 1 */
+	_in_order(tree, (index << 1) + 1);
+}
+
+void in_order(struct binary_tree* tree)
+{
+	_in_order(tree, 1);
+}
+
+int main()
+{
+	struct binary_tree tree;
+
+	fake_a_tree(&tree);
+	in_order(&tree);
+	return 0;
+}