2024/8/27 LeetCode Hot100 LinkedList

src/main/java/com/cool/hot100/linkedlist/LRUCache.java

@@ -0,0 +1,162 @@
+package com.cool.hot100.linkedlist;
+//
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+//
+///**
+// * Created with IntelliJ IDEA.
+// *
+// * @Author: Cool
+// * @Date: 2024/08/27/20:00
+// * @Description:LeetCode Hot100 LinkedList最后一题
+// * DayNumber 1
+// * Hard 2
+// * Level 7
+// */
+//public class LRUCache {
+//    private final int capacity;
+//
+//    private Map<Integer, LRUNode> map = new HashMap<>();
+//    private int size = 0;
+//    private LRUNode sentry;
+//    private LRUNode curNode;
+//
+//    public LRUCache(int capacity) {
+//        this.capacity = capacity;
+//    }
+//
+//    public int get(int key) {
+//        LRUNode returnVal = map.getOrDefault(key, null);
+//        return returnVal == null ? -1 : returnVal.val;
+//    }
+//
+//    public void put(int key, int value) {
+//        if (size < capacity) {
+////            LRUNode lruNode = new LRUNode(value);
+////            curNode.next=lruNode;
+////            curNode=curNode.next;
+//            putList(key, value);
+//            if (size == 0) sentry = curNode;
+////            map.put(key, lruNode);
+//            size++;
+//        } else {
+//            if (exist(key)) {
+//                putList(key, value);
+//            } else {
+//                putList(key, value);
+//                int val = sentry.val;
+//                remove(val);
+//                sentry = sentry.next;
+//            }
+//
+//        }
+//    }
+//
+//    private void remove(int key) {
+//        map.remove(key);
+//    }
+//
+//    private boolean exist(int key) {
+//        return map.containsKey(key);
+//    }
+//
+//    public void putList(int key, int value) {
+//        LRUNode node = new LRUNode(value);
+//        if(curNode==null){
+//            curNode=node;
+//        }else{
+//            curNode.next = node;
+//            curNode = curNode.next;
+//        }
+//        map.put(key, node);
+//    }
+//
+//}
+//
+//class LRUNode {
+//    int val;
+//    LRUNode next;
+//    LRUNode pre;
+//
+//
+//    LRUNode() {
+//    }
+//
+//    LRUNode(int val) {
+//        this.val = val;
+//    }
+//
+//    LRUNode(int val, LRUNode pre, LRUNode next) {
+//        this.val = val;
+//        this.pre = pre;
+//        this.next = next;
+//    }
+//}
+class LRUCache {
+    private static class Node {
+        int key, value;
+        Node prev, next;
+
+        Node(int k, int v) {
+            key = k;
+            value = v;
+        }
+    }
+
+    private final int capacity;
+    private final Node dummy = new Node(0, 0); // 哨兵节点
+    private final Map<Integer, Node> keyToNode = new HashMap<>();
+
+    public LRUCache(int capacity) {
+        this.capacity = capacity;
+        dummy.prev = dummy;
+        dummy.next = dummy;
+    }
+
+    public int get(int key) {
+        Node node = getNode(key);
+        return node != null ? node.value : -1;
+    }
+
+    public void put(int key, int value) {
+        Node node = getNode(key);
+        if (node != null) { // 有这本书
+            node.value = value; // 更新 value
+            return;
+        }
+        node = new Node(key, value); // 新书
+        keyToNode.put(key, node);
+        pushFront(node); // 放在最上面
+        if (keyToNode.size() > capacity) { // 书太多了
+            Node backNode = dummy.prev;
+            keyToNode.remove(backNode.key);
+            remove(backNode); // 去掉最后一本书
+        }
+    }
+
+    private Node getNode(int key) {
+        if (!keyToNode.containsKey(key)) { // 没有这本书
+            return null;
+        }
+        Node node = keyToNode.get(key); // 有这本书
+        remove(node); // 把这本书抽出来
+        pushFront(node); // 放在最上面
+        return node;
+    }
+
+    // 删除一个节点（抽出一本书）
+    private void remove(Node x) {
+        x.prev.next = x.next;
+        x.next.prev = x.prev;
+    }
+
+    // 在链表头添加一个节点（把一本书放在最上面）
+    private void pushFront(Node x) {
+        x.prev = dummy;
+        x.next = dummy.next;
+        x.prev.next = x;
+        x.next.prev = x;
+    }
+}

src/main/java/com/cool/hot100/linkedlist/Num142.java

@@ -2,11 +2,6 @@ package com.cool.hot100.linkedlist;
 
 import org.junit.Test;
 
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
 public class Num142 {
 
 

src/main/java/com/cool/hot100/linkedlist/Num19.java

@@ -2,9 +2,6 @@ package com.cool.hot100.linkedlist;
 
 import org.junit.Test;
 
-import java.util.ArrayList;
-import java.util.List;
-
 public class Num19 {
 
 
@@ -60,4 +57,14 @@ public class Num19 {
         ListNode node1 = new ListNode(2, node);
         removeNthFromEnd(node1, 1);
     }
+    @Test
+    public void test1(){
+        LRUCache cache=new LRUCache(2);
+        cache.put(1,1);
+        cache.put(2,2);
+        cache.get(1);
+        cache.put(3,3);
+        System.out.println(cache.get(2));
+        cache.put(4,4);
+    }
 }

src/main/java/com/cool/hot100/linkedlist/Num23.java

@@ -1,6 +1,5 @@
 package com.cool.hot100.linkedlist;
 
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.stream.Collectors;

src/main/java/com/cool/hot100/linkedlist/Num25.java

@@ -37,7 +37,7 @@ public class Num25 {
 
     }
 
-    private ListNode[] reverse(ListNode head,ListNode next) {
+    private ListNode[] reverse(ListNode head, ListNode next) {
         ListNode node = head;
         ListNode pre = null;
         ListNode nxt=next.next;