A basic tree sort algorithm.

basic_tree_sort.c

/* A Saturday afternoon hack project.
 * Sort integers from stdin using a binary tree.
 * This algorithm is O(n^2) in the worst case though!
 */

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

typedef struct {
  int value;
  struct node_t * left;
  struct node_t * right;
} node_t;

void insert_node(node_t * tree, int value);
node_t * create_node(void);
void destroy_node(node_t * node);

int
main(int argc, char ** argv) {
  node_t * root;
  char buffer[100];
  char * ptr;

  root = create_node();
  ptr = buffer;
  while ((*ptr = getchar()) != EOF) {
    if(*ptr=='\n') {
      *ptr = '\0';
      insert_node(root,atoi(ptr = buffer));
    }
    else {
      ptr++;
    }
  }
  destroy_node(root);
  return 0;
}

void
insert_node(node_t * tree, int value) {
  node_t * node = tree;
  while (node->value != 0) {
    node = (value < (node->value)) ?
      ((node->left != NULL) ? (node->left) : (node->left = create_node())):
      ((node->right != NULL) ? (node->right) : (node->right = create_node()));
  }
  node->value = value;
  return;
}

node_t *
create_node(void) {
  node_t * node = malloc(sizeof(node_t));
  node->value = 0, node->left = NULL, node->right = NULL;
  return node;
}

void
destroy_node(node_t * node) {
  if(node->left != NULL) destroy_node(node->left);
  printf("%d\n", node->value);
  if(node->right != NULL) destroy_node(node->right);
  return free(node);
}