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ECE 2035 final project
Dependencies: mbed wave_player 4DGL-uLCD-SE MMA8452
Diff: hash_table.cpp
- Revision:
- 2:22d36e7740f1
- Parent:
- 0:35660d7952f7
--- a/hash_table.cpp Wed Apr 04 21:11:07 2018 +0000 +++ b/hash_table.cpp Mon Apr 15 12:25:08 2019 +0000 @@ -1,6 +1,6 @@ /* - Student Name: - Date: + Student Name: Nikhil Patel + Date: 11-8-18 ======================= ECE 2035 Project 2-1: @@ -30,7 +30,7 @@ - "HashTableEntry myNewHashTableEntry;" The preceding underscore "_" simply provides a distinction between the names - of the actual struct defition and the "nicknames" that we use to initialize + of the actual struct definition and the "nicknames" that we use to initialize new structs. [See Hidden Definitions section for more information.] @@ -126,7 +126,11 @@ * @return The pointer to the hash table entry */ static HashTableEntry* createHashTableEntry(unsigned int key, void* value) { - + HashTableEntry* node = (HashTableEntry*)malloc(sizeof(HashTableEntry)); + node->value = value; + node->key = key; + node->next = NULL; + return node; } /** @@ -140,7 +144,15 @@ * @return The pointer to the hash table entry, or NULL if key does not exist */ static HashTableEntry* findItem(HashTable* hashTable, unsigned int key) { - + int bucketNum = hashTable->hash(key); + HashTableEntry* this_entry = hashTable->buckets[bucketNum]; + while(this_entry) { + if(this_entry->key == key) { + return this_entry; + } + this_entry = this_entry->next; + } + return NULL; } /**************************************************************************** @@ -167,7 +179,7 @@ newTable->num_buckets = numBuckets; newTable->buckets = (HashTableEntry**)malloc(numBuckets*sizeof(HashTableEntry*)); - // As the new buckets are empty, init each bucket as NULL. + // As the new buckets contain indeterminant values, init each bucket as NULL. unsigned int i; for (i=0; i<numBuckets; ++i) { newTable->buckets[i] = NULL; @@ -178,21 +190,109 @@ } void destroyHashTable(HashTable* hashTable) { - + unsigned int i = 0; //init counter + for(i=0; i<hashTable->num_buckets; ++i){ //loop through each bucket + HashTableEntry* iterator = hashTable->buckets[i]; //start at head of bucket + while(iterator){ //until reach end of linked list at bucket + HashTableEntry* tmp = iterator->next; //store the next node + free(iterator->value); //free the node's value + free(iterator); //free the node itself + iterator = tmp; //restore the next node + } + } + free(hashTable->buckets); //free the buckets + free(hashTable); //free the hash table itself } void* insertItem(HashTable* hashTable, unsigned int key, void* value) { - + HashTableEntry* this_entry = findItem(hashTable,key); //will return a non-NULL value if the key exists + if(this_entry){ //if key already exists + void* replacedVal = this_entry->value; //get the value being replaces + this_entry->value = value; //replace the original value + return replacedVal; //return the value that was replaced + } + else{ //if key doesn't already exist + HashTableEntry* newNode = createHashTableEntry(key,value); //create a new node + int bucketNum = hashTable->hash(key); //get the bucket num where it will be added + if(hashTable->buckets[bucketNum] == NULL){ //if the bucket is empty + hashTable->buckets[bucketNum] = newNode; //the head of the bucket is the new node + return NULL; //return NULL to show nothing was replaced + } + else{ //if the bucket already has a linked list started + HashTableEntry* iterator = hashTable->buckets[bucketNum]; //first node + while(iterator){ //until the end of the linked list + if(iterator->next == NULL){ //reached tail of list + iterator->next = newNode; //place new node at tail + return NULL; //return NULL to show nothing was replaced + } + iterator = iterator->next; //go on to the next node + } + } + } + return NULL; } void* getItem(HashTable* hashTable, unsigned int key) { - + int bucketNum = hashTable->hash(key); //get the bucket number of the item + HashTableEntry* this_entry = hashTable->buckets[bucketNum]; //get the head of the bucket + while(this_entry) { //loop through the bucket's linked list + if(this_entry->key == key) { //if the node's key matches to input + return this_entry->value; //return the matching value + } + this_entry = this_entry->next; //go on to next node + } + return NULL; //No node with such a key } void* removeItem(HashTable* hashTable, unsigned int key) { - + int bucketNum = hashTable->hash(key); //bucket number where item is + HashTableEntry* iterator = hashTable->buckets[bucketNum]; //head of bucket + HashTableEntry* this_entry = findItem(hashTable,key); //get address/NULL of item + if(this_entry == NULL) //key doesnt exist + return NULL; + else{ //key exists + void* val = this_entry->value; //store key's value address + if(iterator == this_entry) { //item is first in linked list + hashTable->buckets[bucketNum] = this_entry->next; //unlink first node from list + free(this_entry); //free the first node + return val; //return the value of node removed + } + else{ //item isn't the first in the linked list + while(iterator){ //iterate through the linked list + if(iterator->next->key == key){ //if next node has key + iterator->next = this_entry->next; //unlink it from the list + free(this_entry); //free it + return val; //return the value of node removed + } + iterator = iterator->next; //go on to next node + } + } + } + return NULL; } void deleteItem(HashTable* hashTable, unsigned int key) { - -} \ No newline at end of file + int bucketNum = hashTable->hash(key); //bucket where item is + HashTableEntry* iterator = hashTable->buckets[bucketNum]; //head of bucket + HashTableEntry* this_entry = findItem(hashTable,key); //get address/NULL of item + if(this_entry == NULL) //key doesnt exist + return; //do nothing + else{ //key exists + if(iterator == this_entry) { // item is first node of linked list + hashTable->buckets[bucketNum] = this_entry->next; //unlink first node from list + free(this_entry->value); //free the node's value + free(this_entry); //free the node + } + else{ //item isn't first node in list + while(iterator){ //iterate through list + if(iterator->next->key == key){ //if next node has key + iterator->next = this_entry->next; //unlink node from list + free(this_entry->value); //free node's value + free(this_entry); //free node + return; + } + iterator = iterator->next; //go to next node + } + } + } +}