Only need one function implemented in C. It's the drop method. Everything else works so it can be tested.  /* * hashmap - Implementation of a lookup table as a hashmap. The table maintains symbol/value * pairs with the symbol being used as the key. * * Example: The pair RED, 12 would use 'RED' in a hashing function to compute * a bin number (or array index) at which the value '12' would be stored. To retrieve a * value from the lookup table, the symbol 'RED' would be used as the key and yield the * the value '12'. If a new pair with the same key is inserted (RED, 23 for example), * the new value replaces the existing value in the hashmap. * * If two symbols hash to the same bin number, a 'collision' occurs. The (symbol, value) pair which * created the collision is then inserted at the START of a linked list for that bin number - i.e. each * bin number points to a unique list of (symbol, value) pairs. * * YOUR NAME GOES HERE * */ #include  #include  #include  #define BINSIZE 11 /* number of hashmap bins (intentionally small to create collisions) */ struct binEntry { struct binEntry *next; /* next entry in the list */ struct binEntry *prev; /* previous entry in the list */ char *symbol; /* defined symbol name */ char *value; /* value of the symbol */ }; static struct binEntry *hashtable[BINSIZE]; /* table of binEntry pointers */ /* this array is visible to all functions in this file */ /************************************************************ hash - Create an unsigned integer hashvalue for a string ( DO NOT EDIT THIS FUNCTION ) ************************************************************/ unsigned int hash( char *s) { unsigned int hashvalue; for( hashvalue= 0; *s != '\0' ; s++) hashvalue = *s + 31 * hashvalue; return hashvalue % BINSIZE; } /******************************************************************** lookup - Given a symbol name, return a binEntry. Return NULL if not found ( DO NOT EDIT THIS FUNCTION ) *******************************************************************/ struct binEntry *lookup( char *symbol) { struct binEntry *entry; for( entry = hashtable[ hash(symbol)] ; entry != NULL ; entry = entry->next) if ( strcmp( symbol, entry->symbol) == 0) return entry; return NULL; } /**************************************************************** insert - Inserts a symbol/value pair into the hashmap. Existing symbols are updated with the new value. A pointer to the new entry is returned. ( DO NOT EDIT THIS FUNCTION ) ***************************************************************/ struct binEntry *insert( char *symbol, char *value) { struct binEntry *entry; unsigned int hashvalue; if (( entry=lookup(symbol)) == NULL ) { /* symbol not found, create new entry */ entry = (struct binEntry*) malloc( sizeof (struct binEntry)); entry->symbol = strdup( symbol); /* create a duplicate of this symbol */ hashvalue = hash( symbol ); entry->next = hashtable[hashvalue]; /* new entries become the start of the chain */ entry->prev = NULL; /* a NULL previous pointer means it is first on the list */ if ( entry->next != NULL ) /* if there is an existing entry in this bin, set its prev pointer */ (entry->next)->prev = entry; hashtable[hashvalue] = entry; /* this entry becomes the head of the list for this bin */ } else { /* symbol exists, just update value */ free( (void*) entry->value); /* release memory for current value being replaced */ } entry->value = strdup( value); /* create a duplicate of the value for this entry */ return entry; } /**************************************************************** drop - Deletes a symbol/value entry from the hashmap. Delete request is ignored if the symbol is not found. ***************************************************************/ void drop( char *symbol ) { /* YOUR CODE GOES HERE */ return; } /************************************************************************** dump - Print the contents of the hashmap ( DO NOT EDIT THIS FUNCTION ) ***************************************************************************/ void dump() { unsigned int bin; struct binEntry *entry; printf(" === Hashmap Contents === "); printf("BIN "); printf("--- "); for( bin=0 ; bin < BINSIZE ; bin++ ) { printf( "%2d ", bin+1); if ( hashtable[bin] == NULL ) printf( "NULL"); else { for( entry = hashtable[bin] ; entry != NULL ; entry = entry->next) { printf("( %s , %s )", entry->symbol, entry->value); if( entry->next != NULL) printf(" --> "); } } printf(" "); } printf(" "); return; } /************************************************************************** main - function main begins program execution - no command line parameters ***************************************************************************/ int main() { struct binEntry tmpEntry; struct binEntry *entry = &tmpEntry; int i; for( i = 0 ; i < BINSIZE ; i++ ) /* initialize each bin to point to an empty list */ hashtable[ i ] = NULL; entry = insert( "RED", "6"); /* GOLD -> BLUE -> RED (same bin) */ entry = insert( "BLUE", "7"); entry = insert( "GOLD", "2"); entry = insert("ORANGE", "3"); /* CYAN -> ORANGE (same bin) */ entry = insert("CYAN", "5"); entry = insert("GREEN", "1"); /* VIOLET -> GREEN (same bin) */ entry = insert("VIOLET", "4"); entry = insert("BLACK", "0"); /* BLACK (single entry) */ dump(); printf("Drop single entry (BLACK)"); drop("BLACK"); dump(); printf("Drop first in list (CYAN)"); drop("CYAN"); dump(); printf("Drop middle of list (BLUE)"); drop("BLUE"); dump(); printf("Drop last in list (GREEN)"); drop("GREEN"); dump(); printf("Drop invalid symbol (BROWN)"); drop("BROWN"); dump(); return 0; /* indicates successful termination */ } /* end main */