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Commit43f86b6

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LRU
1 parent166eb89 commit43f86b6

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2 files changed

+141
-0
lines changed

2 files changed

+141
-0
lines changed

‎hash/LRUCache.java

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packageAlgorithms.hash;
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importjava.util.HashMap;
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publicclassLRUCache {
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privateclassDLink {
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DLinkpre;
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DLinknext;
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intval;
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intkey;
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DLink(intkey,intval) {
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this.val =val;
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this.key =key;
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pre =null;
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next =null;
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}
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}
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HashMap<Integer,DLink>map;
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DLinkhead;
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DLinktail;
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intcapacity;
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publicvoidremoveFist() {
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removeNode(head.next);
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}
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publicvoidremoveNode(DLinknode) {
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node.pre.next =node.next;
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node.next.pre =node.pre;
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}
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// add a node to the tail.
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publicvoidaddToTail(DLinknode) {
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tail.pre.next =node;
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node.pre =tail.pre;
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node.next =tail;
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tail.pre =node;
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}
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publicLRUCache(intcapacity) {
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map =newHashMap<Integer,DLink>();
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// two dummy nodes. In that case, we can deal with them more conviencely.
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head =newDLink(-1, -1);
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tail =newDLink(-1, -1);
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head.next =tail;
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tail.pre =head;
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this.capacity =capacity;
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}
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publicintget(intkey) {
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if (map.get(key) ==null) {
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return -1;
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}
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// update the node.
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DLinknode =map.get(key);
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removeNode(node);
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addToTail(node);
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returnnode.val;
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}
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publicvoidset(intkey,intvalue) {
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DLinknode =map.get(key);
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if (node ==null) {
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// create a node and add the key-node pair into the map.
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node =newDLink(key,value);
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map.put(key,node);
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}else {
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// update the value of the node.
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node.val =value;
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removeNode(node);
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}
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addToTail(node);
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// if the LRU is full, just remove a node.
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if (map.size() >capacity) {
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map.remove(head.next.key);
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removeFist();
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}
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}
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}

‎hash/LRUCache2.java

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packageAlgorithms.hash;
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importjava.util.LinkedHashMap;
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importjava.util.Map;
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publicclassLRUCache2 {
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publicstaticvoidmain(String[]strs) {
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LRUCache2lrc2 =newLRUCache2(2);
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lrc2.set(1,3);
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lrc2.set(2,2);
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lrc2.set(1,4);
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lrc2.set(4,2);
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System.out.println(lrc2.get(1));
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}
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LinkedHashMap<Integer,Integer>map;
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intcapacity;
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publicLRUCache2(finalintcapacity) {
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// create a map.
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map =newLinkedHashMap<Integer,Integer>(capacity) {
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/**
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*
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*/
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privatestaticfinallongserialVersionUID =1L;
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protectedbooleanremoveEldestEntry(Map.Entryeldest) {
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returnsize() >capacity;
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}
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};
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this.capacity =capacity;
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}
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publicintget(intkey) {
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Integerret =map.get(key);
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if (ret ==null) {
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return -1;
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}else {
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map.remove(key);
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map.put(key,ret);
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}
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returnret;
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}
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publicvoidset(intkey,intvalue) {
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map.remove(key);
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map.put(key,value);
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}
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}

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