update at 2022-05-01 15:32:14 by ehlxr

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

@@ -0,0 +1,95 @@
+/*
+ * 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 2022-05-01 14:18.
+ */
+public class FindKthFromEnd {
+    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);
+        head.next.next.next.next.next = new ListNode(6);
+
+        System.out.println(head);
+
+        System.out.println(findKthFromEnd(head, 1));
+        System.out.println(findKthFromEnd2(head, 1));
+    }
+
+    public static ListNode findKthFromEnd(ListNode head, int k) {
+        int n = 0;
+        ListNode node = head;
+        ListNode p = null;
+        while (node != null) {
+            if (p != null) {
+                p = p.next;
+            }
+
+            n++;
+            if (n == k) {
+                p = head;
+            }
+
+            node = node.next;
+        }
+        return p;
+    }
+
+    public static ListNode findKthFromEnd2(ListNode head, int k) {
+        ListNode p = head;
+        ListNode q = head;
+        for (int i = 0; i < k; i++) {
+            q = q.next;
+        }
+        while (q != null) {
+            p = p.next;
+            q = q.next;
+        }
+        return p;
+    }
+
+
+    static class ListNode {
+        int val;
+        ListNode next;
+
+        ListNode(int x) {
+            val = x;
+        }
+
+        @Override
+        public String toString() {
+            return "ListNode{" +
+                    "val=" + val +
+                    ", next=" + next +
+                    '}';
+        }
+    }
+}