From 91fb78752208b66284413a15261751e330af7e36 Mon Sep 17 00:00:00 2001
From: Wei Yang <richard.weiyang@gmail.com>
Date: Sun, 2 Dec 2018 07:46:07 +0800
Subject: [PATCH] BST in c

---
 c-cpp/24_binarysearchtree/bst.c | 197 ++++++++++++++++++++++++++++++++
 1 file changed, 197 insertions(+)
 create mode 100644 c-cpp/24_binarysearchtree/bst.c

diff --git a/c-cpp/24_binarysearchtree/bst.c b/c-cpp/24_binarysearchtree/bst.c
new file mode 100644
index 0000000..7fdfd87
--- /dev/null
+++ b/c-cpp/24_binarysearchtree/bst.c
@@ -0,0 +1,197 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <time.h>
+
+enum child_dir {
+	left_child,
+	right_child,
+	root,
+};
+
+struct node {
+	unsigned long data; 
+	struct node *left;
+	struct node *right;
+};
+
+struct root {
+	struct node *r;
+};
+
+void dump(struct node *node, int level, enum child_dir dir)
+{
+	if (!node)
+		return;
+
+	dump(node->right, level + 1, right_child);
+
+	if (dir == left_child)
+		printf("%*s\n", level*3, "|");
+
+	printf("%*s - %05lu\n", level*3, " ", node->data);
+
+	if (dir == right_child)
+		printf("%*s\n", level*3, "|");
+
+	dump(node->left, level + 1, left_child);
+}
+
+struct node* find(struct root *root, unsigned long data)
+{
+	struct node* n = root->r;
+
+	while (n) {
+		if (n->data == data)
+			return n;
+		if (data < n->data)
+			n = n->left;
+		else
+			n = n->right;
+	}
+
+	return NULL;
+}
+
+struct node* new_node(unsigned long data)
+{
+	struct node *n;
+
+	n = malloc(sizeof(struct node));
+
+	n->data = data;
+	n->left = n->right = NULL;
+	return n;
+}
+
+void insert(struct root *root, struct node *new)
+{
+	struct node *parent;
+
+	if (!root->r) {
+		root->r = new;
+		return;
+	}
+
+	parent = root->r;
+
+	while (true) {
+		/* Don't support duplicate data */
+		if (new->data == parent->data)
+			break;
+
+		if (new->data < parent->data) {
+			if (!parent->left) {
+				parent->left = new;
+				break;
+			}
+			parent = parent->left;
+		} else {
+			if (!parent->right) {
+				parent->right = new;
+				break;
+			}
+			parent = parent->right;
+		}
+	}
+}
+
+struct node* delete(struct root *root, unsigned long data)
+{
+	struct node *n = root->r, **p = &root->r;
+	struct node *child;
+
+	while (n && n->data != data) {
+		if (data < n->data) {
+			p = &n->left;
+			n = n->left;
+		} else {
+			p = &n->right;
+			n = n->right;
+		}
+	}
+
+	if (!n)
+		return NULL;
+	
+	if (n->left && n->right) {
+		struct node *rn = n->right, **rp = &n->right;
+
+		while (rn->left) {
+			rp = &rn->left;
+			rn = rn->left;
+		}
+
+		n->data = rn->data;
+		n = rn;
+		p = rp;
+	}
+
+	child = n->left ? n->left : n->right;
+	*p = child;
+
+	return NULL;
+}
+
+void insert_test()
+{
+	struct root tree;
+	struct node* n;
+
+	tree.r = NULL;
+
+	insert(&tree, new_node(9));
+
+	insert(&tree, new_node(5));
+	insert(&tree, new_node(2));
+	insert(&tree, new_node(8));
+
+	insert(&tree, new_node(18));
+	insert(&tree, new_node(13));
+	insert(&tree, new_node(21));
+	insert(&tree, new_node(20));
+
+	dump(tree.r, 0, root);
+
+	n = find(&tree, 18);
+	if (n && n->data == 18)
+		printf("Get 18\n");
+
+}
+
+void delete_test()
+{
+	struct root tree;
+	struct node* n;
+
+	tree.r = NULL;
+
+	insert(&tree, new_node(9));
+
+	insert(&tree, new_node(5));
+	insert(&tree, new_node(2));
+	insert(&tree, new_node(8));
+
+	insert(&tree, new_node(18));
+	insert(&tree, new_node(13));
+	insert(&tree, new_node(21));
+	insert(&tree, new_node(20));
+
+	dump(tree.r, 0, root);
+
+	delete(&tree, 20);
+	printf("Delete 20\n");
+	dump(tree.r, 0, root);
+
+	delete(&tree, 9);
+	printf("Delete 9\n");
+	dump(tree.r, 0, root);
+}
+
+int main()
+{
+	//insert_test();
+	delete_test();
+	return 0;
+}