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hashTables.js
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hashTables.js
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/**
* Created with JetBrains WebStorm.
* User: elle
* Date: 11/7/13
* Time: 1:30 PM
* To change this template use File | Settings | File Templates.
*/
Algorithms.DataStructures.hashTable = (function () {
var _hashTable = [];
var hashTableSize;
function Item(key, value) {
this.key = key || "empty";
this.value = value || "empty";
this.next = null;
}
function initializeHashTable(size) {
hashTableSize = size || 5;
for (var i = 0; i < hashTableSize; i++) {
_hashTable[i] = new Item();
}
}
function insert(key, value) {
var index = getBucketIndex(key);
if (_hashTable[index].key === "empty") {
_hashTable[index] = new Item(key, value);
} else {
var storedItem = _hashTable[index];
var newItem = new Item(key, value);
while (storedItem.next !== null) {
storedItem = storedItem.next;
}
storedItem.next = newItem;
}
}
function search(key) {
var bucket = getBucketIndex(key);
var storedItem = _hashTable[bucket];
if (storedItem.key === "empty") {
console.log("There is no such key in the hash table");
} else {
while (storedItem !== null) {
if (storedItem.key === key) {
console.log("Value is " + storedItem.value);
return storedItem.value;
}
storedItem = storedItem.next;
}
}
return 0;
}
function deleteItem(key) {
var bucket = getBucketIndex(key);
if (_hashTable[bucket].key === "empty") {
console.log("There is no such key in the hash table");
} else if (_hashTable[bucket].key === key && _hashTable[bucket].next === null) {
_hashTable[bucket].key = "empty";
_hashTable[bucket].value = "empty";
} else if (_hashTable[bucket].key === key) {
_hashTable[bucket] = _hashTable[bucket].next;
} else {
var nextItem = _hashTable[bucket].next;
var prevItem = _hashTable[bucket];
while (nextItem !== null && nextItem.key !== key) {
prevItem = nextItem;
nextItem = prevItem.next;
}
if (nextItem === null) {
console.log("There is no such key in the hash table");
} else {
nextItem = nextItem.next;
prevItem.next = nextItem;
}
}
}
function numberOfItemsInBucket(index) {
var count = 0;
if (_hashTable[index].key !== "empty") {
count++;
var storedItem = _hashTable[index];
while (storedItem.next !== null) {
storedItem = storedItem.next;
count++;
}
}
return count;
}
function printTable() {
var totalItemsInBucket;
for (var i = 0; i < hashTableSize; i++) {
totalItemsInBucket = numberOfItemsInBucket(i);
console.log("-------------------------\n");
console.log("bucket = " + i);
console.log(_hashTable[i].key);
console.log(_hashTable[i].value);
console.log("Total number of items in the bucket = " + totalItemsInBucket);
console.log("-------------------------\n");
}
}
function printItemsPerBucket(index) {
var storedItem = _hashTable[index];
if (storedItem.key === "empty") {
console.log("Bucket is empty");
} else {
console.log("Bucket contains: \n");
while (storedItem !== null) {
console.log("-------------------------\n");
console.log(storedItem.key);
console.log(storedItem.value);
console.log("-------------------------\n");
storedItem = storedItem.next;
}
}
}
function getBucketIndex(key) {
var hashValue = 0;
for (var i = 0, len = key.length; i < len; i++) {
hashValue += key.charCodeAt(i);
}
return hashValue % hashTableSize;
}
return {
createTable: function(size) {
initializeHashTable();
},
hashTableSize: hashTableSize,
insert: insert,
search: search,
delete: deleteItem,
numberOfItemsInBucket: numberOfItemsInBucket,
printTable: printTable,
printItemsPerBucket: printItemsPerBucket
}
}());
var hashTable = Algorithms.DataStructures.hashTable;
hashTable.createTable(5);
hashTable.addItem("New York", "NY");
hashTable.addItem("Miami", "FL");
hashTable.addItem("Chicago", "IL");
hashTable.addItem("Itaka", "NY");
hashTable.addItem("Minneapolis", "MN");
hashTable.addItem("Boston", "MA");
hashTable.addItem("Hoboken", "NJ");
hashTable.printItemsPerBucket(3);