update at 2022-05-04 19:31:51 by ehlxr

budd-common/src/main/java/io/github/ehlxr/algorithm/linkedlist/ReverseKGroup.java

@@ -0,0 +1,92 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright © 2022 xrv <xrv@live.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package io.github.ehlxr.algorithm.linkedlist;
+
+/**
+ * @author ehlxr
+ * @since 2022-05-03 14:26.
+ */
+public class ReverseKGroup {
+    public static void main(String[] args) {
+        ListNode head = new ListNode(1);
+        head.next = new ListNode(2);
+        head.next.next = new ListNode(3);
+        head.next.next.next = new ListNode(4);
+        head.next.next.next.next = new ListNode(5);
+        System.out.println(head);
+        System.out.println(reverseKGroup(head, 2));
+    }
+
+    public static ListNode reverseKGroup(ListNode head, int k) {
+        ListNode p = head;
+        for (int i = 0; i < k; i++) {
+            if (p == null) {
+                return head;
+            }
+            p = p.next;
+        }
+
+        ListNode r = reverseN(head, p);
+        head.next = reverseKGroup(p, k);
+
+        return r;
+    }
+
+    public static ListNode reverseN(ListNode head, ListNode n) {
+        ListNode cur = head, pre = null;
+        while (cur != n) {
+            ListNode next = cur.next;
+            cur.next = pre;
+            pre = cur;
+            cur = next;
+        }
+        return pre;
+    }
+
+    public static class ListNode {
+        int val;
+        ListNode next;
+
+        ListNode() {
+        }
+
+        ListNode(int val) {
+            this.val = val;
+        }
+
+        ListNode(int val, ListNode next) {
+            this.val = val;
+            this.next = next;
+        }
+
+        @Override
+        public String toString() {
+            return "ListNode{" +
+                    "val=" + val +
+                    ", next=" + next +
+                    '}';
+        }
+    }
+}

budd-common/src/main/java/io/github/ehlxr/algorithm/linkedlist/ReverseLinkedList.java

@@ -36,17 +36,53 @@ public class ReverseLinkedList {
         Node node4 = new Node(4, node5);
         Node node3 = new Node(3, node4);
         Node node2 = new Node(2, node3);
-        Node node1 = new Node(1, node2);
-        Node node0 = new Node(0, node1);
-        Node root = new Node(null, node0);
+        Node head = new Node(1, node2);
 
-        Node reverse = reverse(root);
-        // root.print();
+        // Node reverse = reverse(root);
+        // reverse.print();
 
-        reverse.print();
+        // System.out.println(reverseToN(head, node3));
+        // System.out.println(reverseToN(head, 2));
+        System.out.println(reverseFm2N(head, 2, 4));
 
     }
 
+    public static Node reverseToN(Node root, Node n) {
+        Node pre = null, cur = root, tmp = root;
+        while (cur != n) {
+            tmp = cur.next;
+
+            cur.next = pre;
+            pre = cur;
+            cur = tmp;
+        }
+
+        return pre;
+
+    }
+
+    static Node next = null;
+
+    public static Node reverseToN(Node root, int n) {
+        if (n == 1) {
+            next = root.next;
+            return root;
+        }
+
+        Node h = reverseToN(root.next, n - 1);
+        root.next.next = root;
+        root.next = next;
+        return h;
+    }
+
+    public static Node reverseFm2N(Node root, int m, int n) {
+        if (m == 1) {
+            return reverseToN(root, n);
+        }
+        root.next = reverseFm2N(root.next, m - 1, n - 1);
+        return root;
+    }
+
     public static Node reverse(Node root) {
 
         Node pre = null;
@@ -73,17 +109,11 @@ class Node {
         this.value = value;
     }
 
-    public void print() {
-        System.out.println(this);
-        Node tmp = this.next;
-        while (tmp != null) {
-            System.out.println(tmp);
-            tmp = tmp.next;
-        }
-    }
-
     @Override
     public String toString() {
-        return "Node[value=" + this.value + "]";
+        return "Node{" +
+                "value=" + value +
+                ", next=" + next +
+                '}';
     }
 }