diff --git a/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/HashMapLinearProbing.java b/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/HashMapLinearProbing.java deleted file mode 100644 index c8ed333a5..000000000 --- a/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/HashMapLinearProbing.java +++ /dev/null @@ -1,203 +0,0 @@ -package com.thealgorithms.datastructures.hashmap.hashing; - -import java.util.*; - -/** - * This class is an implementation of a hash table using linear probing It uses - * a dynamic array to lengthen the size of the hash table when load factor > .7 - */ -public class HashMapLinearProbing { - - private int hsize; // size of the hash table - private Integer[] buckets; // array representing the table - private Integer AVAILABLE; - private int size; // amount of elements in the hash table - - /** - * Constructor initializes buckets array, hsize, and creates dummy object - * for AVAILABLE - * - * @param hsize the desired size of the hash map - */ - public HashMapLinearProbing(int hsize) { - this.buckets = new Integer[hsize]; - this.hsize = hsize; - this.AVAILABLE = Integer.MIN_VALUE; - this.size = 0; - } - - /** - * The Hash Function takes a given key and finds an index based on its data - * - * @param key the desired key to be converted - * @return int an index corresponding to the key - */ - public int hashing(int key) { - int hash = key % hsize; - if (hash < 0) { - hash += hsize; - } - return hash; - } - - /** - * inserts the key into the hash map by wrapping it as an Integer object - * - * @param key the desired key to be inserted in the hash map - */ - public void insertHash(int key) { - Integer wrappedInt = key; - int hash = hashing(key); - - if (isFull()) { - System.out.println("Hash table is full"); - return; - } - - for (int i = 0; i < hsize; i++) { - if (buckets[hash] == null || buckets[hash] == AVAILABLE) { - buckets[hash] = wrappedInt; - size++; - return; - } - - if (hash + 1 < hsize) { - hash++; - } else { - hash = 0; - } - } - } - - /** - * deletes a key from the hash map and adds an available placeholder - * - * @param key the desired key to be deleted - */ - public void deleteHash(int key) { - Integer wrappedInt = key; - int hash = hashing(key); - - if (isEmpty()) { - System.out.println("Table is empty"); - return; - } - - for (int i = 0; i < hsize; i++) { - if (buckets[hash] != null && buckets[hash].equals(wrappedInt)) { - buckets[hash] = AVAILABLE; - size--; - return; - } - - if (hash + 1 < hsize) { - hash++; - } else { - hash = 0; - } - } - System.out.println("Key " + key + " not found"); - } - - /** - * Displays the hash table line by line - */ - public void displayHashtable() { - for (int i = 0; i < hsize; i++) { - if (buckets[i] == null || buckets[i] == AVAILABLE) { - System.out.println("Bucket " + i + ": Empty"); - } else { - System.out.println( - "Bucket " + i + ": " + buckets[i].toString() - ); - } - } - } - - /** - * Finds the index of location based on an inputed key - * - * @param key the desired key to be found - * @return int the index where the key is located - */ - public int findHash(int key) { - Integer wrappedInt = key; - int hash = hashing(key); - - if (isEmpty()) { - System.out.println("Table is empty"); - return -1; - } - - for (int i = 0; i < hsize; i++) { - try { - if (buckets[hash].equals(wrappedInt)) { - buckets[hash] = AVAILABLE; - return hash; - } - } catch (Exception E) {} - - if (hash + 1 < hsize) { - hash++; - } else { - hash = 0; - } - } - System.out.println("Key " + key + " not found"); - return -1; - } - - private void lengthenTable() { - buckets = Arrays.copyOf(buckets, hsize * 2); - hsize *= 2; - System.out.println("Table size is now: " + hsize); - } - - /** - * Checks the load factor of the hash table if greater than .7, - * automatically lengthens table to prevent further collisions - */ - public void checkLoadFactor() { - double factor = (double) size / hsize; - if (factor > .7) { - System.out.println( - "Load factor is " + factor + ", lengthening table" - ); - lengthenTable(); - } else { - System.out.println("Load factor is " + factor); - } - } - - /** - * isFull returns true if the hash map is full and false if not full - * - * @return boolean is Empty - */ - public boolean isFull() { - boolean response = true; - for (int i = 0; i < hsize; i++) { - if (buckets[i] == null || buckets[i] == AVAILABLE) { - response = false; - break; - } - } - return response; - } - - /** - * isEmpty returns true if the hash map is empty and false if not empty - * - * @return boolean is Empty - */ - public boolean isEmpty() { - boolean response = true; - for (int i = 0; i < hsize; i++) { - if (buckets[i] != null) { - response = false; - break; - } - } - return response; - } -} diff --git a/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/LinearProbingHashMap.java b/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/LinearProbingHashMap.java new file mode 100644 index 000000000..c96da27c0 --- /dev/null +++ b/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/LinearProbingHashMap.java @@ -0,0 +1,141 @@ +package com.thealgorithms.datastructures.hashmap.hashing; + +import java.util.ArrayList; + +/*** + * This class is an implementation of a hash table using linear probing. + * @see Linear Probing Hash Table + * + * @param keys type. + * @param values type. + */ +public class LinearProbingHashMap, Value> extends Map { + private int hsize; // size of the hash table + private Key[] keys; + private Value[] values; + private int size; // amount of elements in the hash table + + public LinearProbingHashMap() { + this(16); + } + + @SuppressWarnings("unchecked") + public LinearProbingHashMap(int size) { + this.hsize = size; + keys = (Key[]) new Comparable[size]; + values = (Value[]) new Object[size]; + } + + @Override + public boolean put(Key key, Value value) { + if (key == null) { + return false; + } + + if (size > hsize / 2) { + resize(2 * hsize); + } + + int keyIndex = hash(key, hsize); + for (; keys[keyIndex] != null; keyIndex = increment(keyIndex)) { + if (key.equals(keys[keyIndex])) { + values[keyIndex] = value; + return true; + } + } + + keys[keyIndex] = key; + values[keyIndex] = value; + size++; + return true; + } + + @Override + public Value get(Key key) { + if (key == null) { + return null; + } + + for (int i = hash(key, hsize); keys[i] != null; i = increment(i)) { + if (key.equals(keys[i])) { + return values[i]; + } + } + + return null; + } + + @Override + public boolean delete(Key key) { + if (key == null || !contains(key)) { + return false; + } + + int i = hash(key, hsize); + while (!key.equals(keys[i])) { + i = increment(i); + } + + keys[i] = null; + values[i] = null; + + i = increment(i); + while (keys[i] != null) { + // delete keys[i] an vals[i] and reinsert + Key keyToRehash = keys[i]; + Value valToRehash = values[i]; + keys[i] = null; + values[i] = null; + size--; + put(keyToRehash, valToRehash); + i = increment(i); + } + + size--; + if (size > 0 && size <= hsize / 8) { + resize(hsize / 2); + } + + return true; + } + + @Override + public boolean contains(Key key) { + return get(key) != null; + } + + @Override + int size() { + return size; + } + + @Override + Iterable keys() { + ArrayList listOfKeys = new ArrayList<>(size); + for (int i = 0; i < hsize; i++) { + if (keys[i] != null) { + listOfKeys.add(keys[i]); + } + } + + listOfKeys.sort(Comparable::compareTo); + return listOfKeys; + } + + private int increment(int i) { + return (i + 1) % hsize; + } + + private void resize(int newSize) { + LinearProbingHashMap tmp = new LinearProbingHashMap<>(newSize); + for (int i = 0; i < hsize; i++) { + if (keys[i] != null) { + tmp.put(keys[i], values[i]); + } + } + + this.keys = tmp.keys; + this.values = tmp.values; + this.hsize = newSize; + } +} diff --git a/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/MainLinearProbing.java b/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/MainLinearProbing.java deleted file mode 100644 index bd75d171a..000000000 --- a/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/MainLinearProbing.java +++ /dev/null @@ -1,69 +0,0 @@ -package com.thealgorithms.datastructures.hashmap.hashing; - -import java.util.Scanner; - -public class MainLinearProbing { - - public static void main(String[] args) { - int choice, key; - - HashMapLinearProbing h = new HashMapLinearProbing(7); - Scanner In = new Scanner(System.in); - - while (true) { - System.out.println("Enter your Choice :"); - System.out.println("1. Add Key"); - System.out.println("2. Delete Key"); - System.out.println("3. Print Table"); - System.out.println("4. Exit"); - System.out.println("5. Search and print key index"); - System.out.println("6. Check load factor"); - - choice = In.nextInt(); - - switch (choice) { - case 1: - { - System.out.println("Enter the Key: "); - key = In.nextInt(); - h.insertHash(key); - break; - } - case 2: - { - System.out.println("Enter the Key delete: "); - key = In.nextInt(); - h.deleteHash(key); - break; - } - case 3: - { - System.out.println("Print table"); - h.displayHashtable(); - break; - } - case 4: - { - In.close(); - return; - } - case 5: - { - System.out.println( - "Enter the Key to find and print: " - ); - key = In.nextInt(); - System.out.println( - "Key: " + key + " is at index: " + h.findHash(key) - ); - break; - } - case 6: - { - h.checkLoadFactor(); - break; - } - } - } - } -} diff --git a/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/Map.java b/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/Map.java new file mode 100644 index 000000000..cd27b0a79 --- /dev/null +++ b/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/Map.java @@ -0,0 +1,23 @@ +package com.thealgorithms.datastructures.hashmap.hashing; + +public abstract class Map { + + abstract boolean put(Key key, Value value); + + abstract Value get(Key key); + + abstract boolean delete(Key key); + + abstract Iterable keys(); + + abstract int size(); + + public boolean contains(Key key) { + return get(key) != null; + } + + protected int hash(Key key, int size) { + return (key.hashCode() & Integer.MAX_VALUE) % size; + } + +} diff --git a/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/LinearProbingHashMapTest.java b/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/LinearProbingHashMapTest.java new file mode 100644 index 000000000..d0a72a150 --- /dev/null +++ b/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/LinearProbingHashMapTest.java @@ -0,0 +1,8 @@ +package com.thealgorithms.datastructures.hashmap.hashing; + +class LinearProbingHashMapTest extends MapTest { + @Override + , Value> Map getMap() { + return new LinearProbingHashMap<>(); + } +} diff --git a/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/MapTest.java b/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/MapTest.java new file mode 100644 index 000000000..5ccbcc304 --- /dev/null +++ b/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/MapTest.java @@ -0,0 +1,129 @@ +package com.thealgorithms.datastructures.hashmap.hashing; + +import org.junit.jupiter.api.Test; + +import java.util.Random; + +import static org.junit.jupiter.api.Assertions.*; + +abstract class MapTest { + abstract , Value> Map getMap(); + + @Test + void putTest() { + Map map = getMap(); + + assertFalse(map.put(null, "-25")); + assertFalse(map.put(null, null)); + assertTrue(map.put(-25, "-25")); + assertTrue(map.put(33, "33")); + assertTrue(map.put(100, "100")); + assertTrue(map.put(100, "+100")); + assertTrue(map.put(100, null)); + } + + @Test + void getTest() { + Map map = getMap(); + for (int i = -100; i < 100; i++) { + map.put(i, String.valueOf(i)); + } + + for (int i = -100; i < 100; i++) { + assertEquals(map.get(i), String.valueOf(i)); + } + + for (int i = 100; i < 200; i++) { + assertNull(map.get(i)); + } + + assertNull(map.get(null)); + } + + @Test + void deleteTest() { + Map map = getMap(); + for (int i = -100; i < 100; i++) { + map.put(i, String.valueOf(i)); + } + + for (int i = 0; i < 100; i++) { + assertTrue(map.delete(i)); + } + + for (int i = 100; i < 200; i++) { + assertFalse(map.delete(i)); + } + + assertFalse(map.delete(null)); + } + + @Test + void containsTest() { + Map map = getMap(); + for (int i = -100; i < 100; i++) { + map.put(i, String.valueOf(i)); + } + + for (int i = -50; i < 50; i++) { + assertTrue(map.contains(i)); + } + + for (int i = 100; i < 200; i++) { + assertFalse(map.contains(i)); + } + + assertFalse(map.contains(null)); + } + + @Test + void sizeTest() { + Map map = getMap(); + assertEquals(map.size(), 0); + + for (int i = -100; i < 100; i++) { + map.put(i, String.valueOf(i)); + } + + assertEquals(map.size(), 200); + + for (int i = -50; i < 50; i++) { + map.delete(i); + } + + assertEquals(map.size(), 100); + } + + @Test + void keysTest() { + Map map = getMap(); + Iterable keys = map.keys(); + assertFalse(keys.iterator().hasNext()); + + for (int i = 100; i > -100; i--) { + map.put(i, String.valueOf(i)); + } + + keys = map.keys(); + int i = -100; + for (Integer key : keys) { + assertEquals(key, ++i); + } + } + + @Test + void hashTest() { + Map map = getMap(); + int testSize = 100; + Random random = new Random(); + for (int i = 0; i < 1000; i++) { + int randomInt = random.nextInt(); + int hashIndex = map.hash(randomInt, testSize); + int negateHashIndex = map.hash(-randomInt, testSize); + assertTrue(hashIndex >= 0); + assertTrue(hashIndex < testSize); + assertTrue(negateHashIndex >= 0); + assertTrue(negateHashIndex < testSize); + } + } +}