# C > Data Structures Code Examples

## Basic binary search tree routines

``` Basic binary search tree routines #include <stdio.h> #include <stdlib.h> struct tnode { int data; struct tnode *left; struct tnode *right; }; /* insert, swap, search value, search minimum and search maximum values */ struct tnode *tnode_insert(struct tnode *p, int value); struct tnode *tnode_swap(struct tnode *p); struct tnode *tnode_search(struct tnode *p, int key); struct tnode *tnode_searchmin(struct tnode *p); struct tnode *tnode_searchmax(struct tnode *p); /* destroy, count tree nodes */ void tnode_destroy(struct tnode *p); int tnode_count(struct tnode *p); /* print binary tree inorder, preorder, postorder [recursive] */ void print_inorder(struct tnode *p); void print_preorder(struct tnode *p); void print_postorder(struct tnode *p); int main(void) { int demo_nr[] = {1, 3, 4, 7, 2, 9, 9, 0, 5, 6, 8, 7, 1, 2, 4}; struct tnode *root = NULL; struct tnode *searchval = NULL; int querry = 0; int i = 0; /* demo: insert some nr's into the binary tree */ for(i = 0; i < 15; i++) root = tnode_insert(root, demo_nr[i]); printf("=-=-=\n"); printf("Total number of tree nodes: %d\n", tnode_count(root)); printf("inorder : "); print_inorder(root); printf("\n"); printf("preorder : "); print_preorder(root); printf("\n"); printf("postorder: "); print_postorder(root); printf("\n"); printf("=-=-=\n"); printf("Enter integer, find: "); scanf("%d", &querry); searchval = tnode_search(root, querry); if(searchval == NULL) printf(" * %d Not! found in btree\n", querry); else printf(" * Found! %d in btree\n", searchval->data); searchval = NULL; printf("Searching for Minimum value\n"); searchval = tnode_searchmin(root); if(searchval == NULL) printf(" * Minimum Not! found in btree ?\n"); else printf(" * Found! minimum value %d in btree\n", searchval->data); searchval = NULL; printf("Searching for Maximum value\n"); searchval = tnode_searchmax(root); if(searchval == NULL) printf(" * Maximum Not! found in btree ?\n"); else printf(" * Found! Maximum value %d in btree\n", searchval->data); printf("=-=-=\n"); printf("Exchanging all tree nodes: left <-> right\n"); root = tnode_swap(root); printf("inorder : "); print_inorder(root); printf("\n"); printf("preorder : "); print_preorder(root); printf("\n"); printf("postorder: "); print_postorder(root); printf("\n"); printf("=-=-=\n"); printf("Destroying btree... bye!\n"); tnode_destroy(root); return 0; } /* insert a tnode into the binary tree */ struct tnode *tnode_insert(struct tnode *p, int value) { struct tnode *tmp_one = NULL; struct tnode *tmp_two = NULL; if(p == NULL) { /* insert [new] tnode as root node */ p = (struct tnode *)malloc(sizeof(struct tnode)); p->data = value; p->left = p->right = NULL; } else { tmp_one = p; /* Traverse the tree to get a pointer to the specific tnode */ /* The child of this tnode will be the [new] tnode */ while(tmp_one != NULL) { tmp_two = tmp_one; if(tmp_one ->data > value) tmp_one = tmp_one->left; else tmp_one = tmp_one->right; } if(tmp_two->data > value) { /* insert [new] tnode as left child */ tmp_two->left = (struct tnode *)malloc(sizeof(struct tnode)); tmp_two = tmp_two->left; tmp_two->data = value; tmp_two->left = tmp_two->right = NULL; } else { /* insert [new] tnode as left child */ tmp_two->right = (struct tnode *)malloc(sizeof(struct tnode)); tmp_two = tmp_two->right; tmp_two->data = value; tmp_two->left = tmp_two->right = NULL; } } return(p); } /* print binary tree inorder */ void print_inorder(struct tnode *p) { if(p != NULL) { print_inorder(p->left); printf("%d ", p->data); print_inorder(p->right); } } /* print binary tree preorder */ void print_preorder(struct tnode *p) { if(p != NULL) { printf("%d ", p->data); print_preorder(p->left); print_preorder(p->right); } } /* print binary tree postorder */ void print_postorder(struct tnode *p) { if(p != NULL) { print_postorder(p->left); print_postorder(p->right); printf("%d ", p->data); } } /* returns the total number of tree nodes */ int tnode_count(struct tnode *p) { if(p == NULL) return 0; else { if(p->left == NULL && p->right == NULL) return 1; else return(1 + (tnode_count(p->left) + tnode_count(p->right))); } } /* exchange all left and right tnodes */ struct tnode *tnode_swap(struct tnode *p) { struct tnode *tmp_one = NULL; struct tnode *tmp_two = NULL; if(p != NULL) { tmp_one = tnode_swap(p->left); tmp_two = tnode_swap(p->right); p->right = tmp_one; p->left = tmp_two; } return(p); } /* locate a value in the btree */ struct tnode *tnode_search(struct tnode *p, int key) { struct tnode *temp; temp = p; while(temp != NULL) { if(temp->data == key) return temp; else if(temp->data > key) temp = temp->left; else temp = temp->right; } return NULL; } /* locate a minimum value in the btree */ struct tnode *tnode_searchmin(struct tnode *p) { if(p == NULL) return NULL; else if(p->left == NULL) return p; else return tnode_searchmin(p->left); } /* locate a maximum value in the btree */ struct tnode *tnode_searchmax(struct tnode *p) { if(p != NULL) while(p->right != NULL) p = p->right; return p; } /* destroy the binary tree */ void tnode_destroy(struct tnode *p) { if(p != NULL) { tnode_destroy(p->left); tnode_destroy(p->right); free(p); } } ```