/*
  Student Name:
  Student NETID:
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  Problems Solved:
*/


/*
PROGRAM  : ohash.c
PURPOSE  : insert/delete into an open hash table with doubly-linked lists and no headers
UNIX COMP: gcc -o ohash ohash.c
PC COMP  : TURBO C++ (tcc) or Borland
TEST     : ohash ohash.dat
INTERACT : ohash
REDIRECT : ohash <ohash.dat
HELP     : h(elp; q(uit; c(reate size; i(nsert x; d(isplay; D(elete x
NOTE     : `x' is an integer
EXERCISES: Ex1..4
*/

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

#define N 7

typedef int element_type;
typedef struct list_node *node_ptr;

struct list_node {
  node_ptr next;
  node_ptr prev;
  element_type key;
};

node_ptr hashtable[N];

/* Ex1 : initialize the hash table */
void init_hash() {
}

int hash(int x) {
  return (x % N);
}

/* Ex2 : find the key in the list. return NULL if not found */
node_ptr find_hash(element_type key) {
  return NULL;
}


/* Ex3 : insert the key into the list. return 0 if there is a duplicate,
         otherwise, insert at the head and return 1. Maintain both next and prev
         pointers */

int insert_hash(element_type key) {
  return 0;
}

/* Ex4 : delete the key from the list. return 0 if it doesn't exist,
         otherwise, delete and return 1. Maintain both next and prev
         pointers. */

int delete_hash(element_type key) {
  return 0;
}

void display_hash() {
int i;
node_ptr p;
  printf("\nOpen Hash Table:\n");
  for (i=0; i<N; i++) {
    printf("    +-+\n");  
    printf("%3d | |",i);
    p = hashtable[i];
    while (p != NULL) {
      printf("-> %d ",p->key);
      p = p->next;
    }
    printf("\n");
  }
  printf("    +-+\n");  
}

void cmd_interpreter(FILE *fp) {
char cmd, xtra;
element_type x;

  init_hash();
  printf("> ");
  while (fscanf(fp,"%c",&cmd) != EOF) {
    switch (cmd) {
      case 'q' : exit(0);
      case 'h' : printf("h(elp; q(uit; i(nsert x; d(isplay; D(elete x\n");
                 break;
      case 'i' : fscanf(fp,"%d",&x);
                 insert_hash(x);
                 break;
      case 'D' : fscanf(fp,"%d",&x);
                 delete_hash(x);
                 break;
      case 'd' : display_hash();
                 break;
    }
    fscanf(fp,"%c",&xtra);
    printf("> ");
  }
}

 
int main(int argc, char *argv[]) {
FILE *fp;
  if (argc == 1)
    fp = stdin;
  else {
    fp = fopen(argv[1],"r");
    if (fp == NULL) {
      printf("No File: %s\n",argv[1]);
      return 1;
    }
  }
  cmd_interpreter(fp);
  return 0;
}