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

void lowercase(char * word)
{ int i;
  for (i = 0; 1; i += 1)
  { if (word[i] == '\0')
      break;
    word[i] = tolower(word[i]); } }

struct node
{ char * string;
  int count;
  struct node * left, * right; };

struct node * make_node(char * s, int c)
{ struct node * n = (struct node *)malloc(sizeof(struct node));
  n->string = s;
  n->count = c;
  n->left = NULL;
  n->right = NULL;
  return n; }

void print(struct node * t)
{ if (t == NULL)
    return;
  print(t->left);
  printf("%s occurs %d times\n", t->string, t->count);
  print(t->right); }

void add(char * word, struct node * * root)
{ int r;
  if (*root == NULL)
  { *root = make_node(word, 1);
    return; }
  r = strcmp(word, (*root)->string);
  if (r < 0)
    add(word, &(*root)->left);
  else if (r == 0)
    (*root)->count += 1;
  else
    add(word, &(*root)->right); }

// use a.out filename to run
int main(int argc, char * argv[])
{ FILE * fin;
  struct node * tree = NULL;
  if (argc != 2)
  { printf("error: give filename on command line\n");
    exit(1); }
  fin = fopen(argv[1], "r");
  if (fin == NULL)
  { printf("file %s does not exist\n", argv[1]);
    exit(1); }

  while (1)
  { char s[100];
    int n = fscanf(fin, "%s", s);
    if (n != 1)
      break;
    lowercase(s);
    printf("read \"%s\"\n", s);
    add(strdup(s), & tree); }
  print(tree); }