tree.c

#include <stdio.h>
#include <stdlib.h>

struct _Node {
	struct _Node *left;
	int val;
	struct _Node *right;
};

typedef struct _Node Node;

Node * NewNode(int val)  {
	Node *node =  malloc(sizeof(Node));
	node->left = NULL;
	node->val = val;
	node->right = NULL;
	return node;
}

void AddValue(Node *node, int val) {
	if (val <= node->val) {
		if (node->left == NULL)  {
			node->left = NewNode(val);	
		} else {
			AddValue(node->left, val);
		}
		return;
	}
	if (node->right == NULL){
		node->right = NewNode(val);
	} else {
		AddValue(node->right, val);
	}
	return;
}

void DeleteNode(Node *node) {
	if (node->left != NULL) {
		DeleteNode(node->left);
	}
	if (node->right != NULL) {
		DeleteNode(node->right);
	}
	free(node);
}

int main() {
	Node *root = NewNode(2);
	
	AddValue(root, 20);
	AddValue(root, 1);
	AddValue(root, 0);
	AddValue(root, 21);

	printf("main root %d\n", root->val);
	printf("left root %d\n", root->left->val);
	printf("right root %d\n", root->right->val);
	printf("left of left root %d\n", root->left->left->val);
	printf("right of right root %d\n", root->right->right->val);

	DeleteNode(root);
}