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Merged
siriak merged 5 commits into from
Oct 28, 2021
Merged

add MRU Implementation #2738

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ef6f729
add MRU Implementation
januslinhc Oct 25, 2021
49eed07
add MRU Implementation; Fixes: #2736
januslinhc Oct 25, 2021
7b29712
add MRU Implementation; Fixes: #2736
januslinhc Oct 25, 2021
89b201d
Merge branch 'master' into feature/MRU_Implementation
siriak Oct 28, 2021
589415d
Update directory
Oct 28, 2021
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8 changes: 8 additions & 0 deletions DIRECTORY.md
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* [IIRFilter](https://github.com/TheAlgorithms/Java/blob/master/AudioFilters/IIRFilter.java)

## Backtracking
* [KnightsTour](https://github.com/TheAlgorithms/Java/blob/master/Backtracking/KnightsTour.java)
* [NQueens](https://github.com/TheAlgorithms/Java/blob/master/Backtracking/NQueens.java)
* [PowerSum](https://github.com/TheAlgorithms/Java/blob/master/Backtracking/PowerSum.java)

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* [CircularBuffer](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Buffers/CircularBuffer.java)
* Caches
* [LRUCache](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Caches/LRUCache.java)
* [MRUCache](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Caches/MRUCache.java)
* DisjointSets
* [DisjointSets](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/DisjointSets/DisjointSets.java)
* [Node](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/DisjointSets/Node.java)
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* Lists
* [CircleLinkedList](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/CircleLinkedList.java)
* [CountSinglyLinkedListRecursion](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/CountSinglyLinkedListRecursion.java)
* [CreateAndDetectLoop](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/CreateAndDetectLoop.java)
* [CursorLinkedList](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/CursorLinkedList.java)
* [DoublyLinkedList](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/DoublyLinkedList.java)
* [Merge K SortedLinkedlist](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/Merge_K_SortedLinkedlist.java)
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* [BSTRecursive](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/BSTRecursive.java)
* [BSTRecursiveGeneric](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/BSTRecursiveGeneric.java)
* [CeilInBinarySearchTree](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/CeilInBinarySearchTree.java)
* [CreateBinaryTreeFromInorderPreorder](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/CreateBinaryTreeFromInorderPreorder.java)
* [CreateBSTFromSortedArray](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/CreateBSTFromSortedArray.java)
* [FenwickTree](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/FenwickTree.java)
* [GenericTree](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/GenericTree.java)
* [LCA](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/LCA.java)
* [LevelOrderTraversal](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/LevelOrderTraversal.java)
* [LevelOrderTraversalQueue](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/LevelOrderTraversalQueue.java)
* [nearestRightKey](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/nearestRightKey.java)
* [PrintTopViewofTree](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/PrintTopViewofTree.java)
* [RedBlackBST](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/RedBlackBST.java)
* [SegmentTree](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/SegmentTree.java)
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## Others
* [BestFit](https://github.com/TheAlgorithms/Java/blob/master/Others/BestFit.java)
* [BFPRT](https://github.com/TheAlgorithms/Java/blob/master/Others/BFPRT.java)
* [BoyerMoore](https://github.com/TheAlgorithms/Java/blob/master/Others/BoyerMoore.java)
* [BrianKernighanAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/Others/BrianKernighanAlgorithm.java)
* [CountChar](https://github.com/TheAlgorithms/Java/blob/master/Others/CountChar.java)
* [CountWords](https://github.com/TheAlgorithms/Java/blob/master/Others/CountWords.java)
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* [SquareRootBinarySearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/SquareRootBinarySearch.java)
* [TernarySearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/TernarySearch.java)
* [UnionFind](https://github.com/TheAlgorithms/Java/blob/master/Searches/UnionFind.java)
* [UpperBound](https://github.com/TheAlgorithms/Java/blob/master/Searches/UpperBound.java)

## Sorts
* [BitonicSort](https://github.com/TheAlgorithms/Java/blob/master/Sorts/BitonicSort.java)
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179 changes: 179 additions & 0 deletions DataStructures/Caches/MRUCache.java
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package DataStructures.Caches;

import java.util.HashMap;
import java.util.Map;

/**
* Most recently used (MRU)
* <p>
* In contrast to Least Recently Used (LRU), MRU discards the most recently used items first.
* https://en.wikipedia.org/wiki/Cache_replacement_policies#Most_recently_used_(MRU)
*
* @param <K> key type
* @param <V> value type
*/
public class MRUCache<K, V> {
private final Map<K, Entry<K, V>> data = new HashMap<>();
private Entry<K, V> head;
private Entry<K, V> tail;
private int cap;
private static final int DEFAULT_CAP = 100;

public MRUCache() {
setCapacity(DEFAULT_CAP);
}

private void setCapacity(int newCapacity) {
checkCapacity(newCapacity);
for (int i = data.size(); i > newCapacity; i--) {
Entry<K, V> evicted = evict();
data.remove(evicted.getKey());
}
this.cap = newCapacity;
}


private void checkCapacity(int capacity) {
if (capacity <= 0) {
throw new RuntimeException("capacity must greater than 0!");
}
}

private Entry<K, V> evict() {
if (head == null) {
throw new RuntimeException("cache cannot be empty!");
}
final Entry<K, V> evicted = this.tail;
tail = evicted.getPreEntry();
tail.setNextEntry(null);
evicted.setNextEntry(null);
return evicted;
}

public MRUCache(int cap) {
setCapacity(cap);
}

public V get(K key) {
if (!data.containsKey(key)) {
return null;
}
final Entry<K, V> entry = data.get(key);
moveEntryToLast(entry);
return entry.getValue();
}

public void put(K key, V value) {
if (data.containsKey(key)) {
final Entry<K, V> exitingEntry = data.get(key);
exitingEntry.setValue(value);
moveEntryToLast(exitingEntry);
return;
}
Entry<K, V> newEntry;
if (data.size() == cap) {
newEntry = evict();
data.remove(newEntry.getKey());
} else {
newEntry = new Entry<>();
}
newEntry.setKey(key);
newEntry.setValue(value);
addNewEntry(newEntry);
data.put(key, newEntry);
}

private void addNewEntry(Entry<K, V> newEntry) {
if (data.isEmpty()) {
head = newEntry;
tail = newEntry;
return;
}
tail.setNextEntry(newEntry);
newEntry.setPreEntry(tail);
newEntry.setNextEntry(null);
tail = newEntry;
}

private void moveEntryToLast(Entry<K, V> entry) {
if (tail == entry) {
return;
}
final Entry<K, V> preEntry = entry.getPreEntry();
final Entry<K, V> nextEntry = entry.getNextEntry();
if (preEntry != null) {
preEntry.setNextEntry(nextEntry);
}
if (nextEntry != null) {
nextEntry.setPreEntry(preEntry);
}
if (head == entry) {
head = nextEntry;
}
tail.setNextEntry(entry);
entry.setPreEntry(tail);
entry.setNextEntry(null);
tail = entry;
}

static final class Entry<I, J> {
private Entry<I, J> preEntry;
private Entry<I, J> nextEntry;
private I key;
private J value;

public Entry() {
}

public Entry(Entry<I, J> preEntry, Entry<I, J> nextEntry, I key, J value) {
this.preEntry = preEntry;
this.nextEntry = nextEntry;
this.key = key;
this.value = value;
}

public Entry<I, J> getPreEntry() {
return preEntry;
}

public void setPreEntry(Entry<I, J> preEntry) {
this.preEntry = preEntry;
}

public Entry<I, J> getNextEntry() {
return nextEntry;
}

public void setNextEntry(Entry<I, J> nextEntry) {
this.nextEntry = nextEntry;
}

public I getKey() {
return key;
}

public void setKey(I key) {
this.key = key;
}

public J getValue() {
return value;
}

public void setValue(J value) {
this.value = value;
}
}

public static void main(String[] args) {
final MRUCache<String, Integer> cache = new MRUCache<>(2);
cache.put("Key1", 1);
cache.put("Key2", 2);
cache.put("Key3", 3);
cache.put("Key4", 4);
System.out.println("getValue(Key1): " + cache.get("Key1"));
System.out.println("getValue(Key2): " + cache.get("Key2"));
System.out.println("getValue(Key3): " + cache.get("Key3"));
System.out.println("getValue(Key4): " + cache.get("Key4"));
}
}