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链表其他解法
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7 files changed

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‎src/main/java/com/chen/algorithm/study/test141/Solution1.java‎

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*
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* @author : chen weijie
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* @Date: 2019-11-02 15:58
8-
* @Description: zhunn 判断链表是否有环
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*/
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public class Solution1 {
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‎src/main/java/com/chen/algorithm/study/test141/Solution3.java‎

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package com.chen.algorithm.study.test141;
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import java.util.HashSet;
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import java.util.Set;
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/**
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* @Auther: zhunn
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* @Date: 2020/10/23 16:26
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* @Description: 环形链表一：判断链表是否有环
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* 方法：1-哈希表，2-快慢指针
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*/
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public class Solution3 {
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class ListNode {
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int val;
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ListNode next;
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ListNode(int x) {
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val = x;
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next = null;
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}
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}
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/**
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* 2-快慢指针
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* @param head
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* @return
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*/
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public boolean hasCycle1(ListNode head) {
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if (head == null || head.next == null) {
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return false;
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}
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ListNode slow = head;
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ListNode fast = head;
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while (fast != null && fast.next != null) {
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slow = slow.next;
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fast = fast.next.next;
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if (slow == fast) {
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return true;
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}
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}
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return false;
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}
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/**
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* 1-哈希表
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* @param head
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* @return
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*/
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public boolean hasCycle2(ListNode head) {
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if (head == null || head.next == null) {
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return false;
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}
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ListNode dummy = head;
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Set<ListNode> visited = new HashSet<>();
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while (dummy != null) {
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if (visited.contains(dummy)) {
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return true;
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} else {
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visited.add(dummy);
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}
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dummy = dummy.next;
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}
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return false;
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}
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/**
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* 1-哈希表简易版
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* @param head
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* @return
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*/
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public boolean hasCycle3(ListNode head) {
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Set<ListNode> seen = new HashSet<>();
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while (head != null) {
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if (!seen.add(head)) {
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return true;
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}
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head = head.next;
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}
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return false;
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}
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}

‎src/main/java/com/chen/algorithm/study/test142/Solution4.java‎

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package com.chen.algorithm.study.test142;
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import java.util.HashSet;
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import java.util.Set;
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/**
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* @Auther: zhunn
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* @Date: 2020/10/23 16:10
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* @Description: 环形链表二，找出入环点
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* 方法：1-哈希表，2-快慢指针
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*/
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public class Solution4 {
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/**
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* 1-哈希表
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* @param head
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* @return
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*/
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public ListNode detectCycle1(ListNode head) {
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if (head == null || head.next == null) {
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return null;
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}
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ListNode dummy = head;
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Set<ListNode> visited = new HashSet<>();
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while (dummy != null) {
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if (visited.contains(dummy)) {
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return dummy;
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} else {
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visited.add(dummy);
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}
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dummy = dummy.next;
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}
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return null;
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}
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/**
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* 2-快慢指针
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* @param head
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* @return
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*/
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public ListNode detectCycle2(ListNode head) {
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if (head == null || head.next == null) {
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return null;
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}
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ListNode slow = head;
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ListNode fast = head;
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while (fast != null && fast.next != null) {
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slow = slow.next;
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fast = fast.next.next;
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if (slow == fast) {
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break;
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}
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}
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ListNode ptr = head;
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while (slow != ptr) {
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slow = slow.next;
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ptr = ptr.next;
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}
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return slow;
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}
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}

‎src/main/java/com/chen/algorithm/study/test160/Solution.java‎

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package com.chen.algorithm.study.test160;
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import org.junit.Test;
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/**
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* @author : chen weijie
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* @Date: 2019-11-02 17:40
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* @Description: zhunn 相交链表
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*/
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public class Solution {
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return b;
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}
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@Test
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public void test() {
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ListNode l1_1 = new ListNode(4);
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ListNode l1_2 = new ListNode(1);
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ListNode l1_3 = new ListNode(8);
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ListNode l1_4 = new ListNode(7);
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ListNode l1_5 = new ListNode(5);
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ListNode l2_1 = new ListNode(5);
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ListNode l2_2 = new ListNode(0);
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ListNode l2_3 = new ListNode(1);
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l1_1.next = l1_2;
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l1_2.next = l1_3;
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l1_3.next = l1_4;
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l1_4.next = l1_5;
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l2_1.next = l2_2;
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l2_2.next = l2_3;
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l2_3.next = l1_3;
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ListNode result = getIntersectionNode(l1_1, l2_1);
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while (result != null) {
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System.out.println(result.val);
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result = result.next;
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}
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}
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}

‎src/main/java/com/chen/algorithm/study/test24/Solution3.java‎

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package com.chen.algorithm.study.test24;
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import org.junit.Test;
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/**
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* @Auther: zhunn
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* @Date: 2020/10/23 10:48
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* @Description: 两两交换链表中结点：1-递归，2-迭代
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*/
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public class Solution3 {
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/**
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* 1-递归
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* @param head
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* @return
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*/
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public ListNode swapPairs1(ListNode head) {
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if (head == null || head.next == null) {
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return head;
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}
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ListNode newHead = head.next;
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head.next = swapPairs1(newHead.next);
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newHead.next = head;
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return newHead;
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}
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/**
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* 2-迭代
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* @param head
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* @return
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*/
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public ListNode swapPairs2(ListNode head) {
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if (head == null || head.next == null) {
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return head;
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}
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ListNode dummyHead = new ListNode(-1);
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dummyHead.next = head;
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ListNode temp = dummyHead;
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while (temp.next != null && temp.next.next != null) {
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ListNode node1 = temp.next;
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ListNode node2 = temp.next.next;
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temp.next = node2;
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node1.next = node2.next;
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node2.next = node1;
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temp = node1;
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}
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return dummyHead.next;
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}
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/**
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* 2-迭代（操作head）
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* @param head
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* @return
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*/
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public ListNode swapPairs3(ListNode head) {
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if (head == null || head.next == null) {
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return head;
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}
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ListNode dummyHead = new ListNode(-1);
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dummyHead.next = head;
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ListNode temp = dummyHead;
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while (head != null && head.next != null) {
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ListNode node1 = head;
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ListNode node2 = head.next;
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temp.next = node2;
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node1.next = node2.next;
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node2.next = node1;
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temp = node1;
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head = node1.next;
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}
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return dummyHead.next;
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}
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@Test
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public void test() {
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ListNode l1_1 = new ListNode(1);
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ListNode l1_2 = new ListNode(2);
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ListNode l1_3 = new ListNode(3);
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ListNode l1_4 = new ListNode(4);
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ListNode l1_5 = new ListNode(5);
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l1_1.next = l1_2;
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l1_2.next = l1_3;
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l1_3.next = l1_4;
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l1_4.next = l1_5;
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ListNode result = swapPairs3(l1_1);
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System.out.println(result.val);
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System.out.println(result.next.val);
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System.out.println(result.next.next.val);
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System.out.println(result.next.next.next.val);
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System.out.println(result.next.next.next.next.val);
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}
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}

‎src/main/java/com/chen/algorithm/study/test242/Solution.java‎

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/**
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* @author : chen weijie
77
* @Date: 2020-05-03 22:12
8+
* @Description: zhunn 有效的字母异位词。哈希表
89
*/
910
public class Solution {
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1112
public boolean isAnagram(String s, String t) {
1213

13-
if (s.length() != t.length()) {
14+
if (s == null || t == null || s.length() != t.length()) {
1415
return false;
1516
}
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17-
int [] counter = new int[26];
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int[] counter = new int[26];
1819
for (int i = 0; i < s.length(); i++) {
1920
counter[s.charAt(i) - 'a']++;
2021
counter[t.charAt(i) - 'a']--;
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3233
@Test
33-
public void testCase(){
34+
public void testCase() {
3435

35-
System.out.println(isAnagram("anagram","nagaram"));
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System.out.println(isAnagram("anagram", "nagaram"));
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}
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}

‎src/main/java/com/chen/algorithm/study/test92/Solution2.java‎

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package com.chen.algorithm.study.test92;
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33

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import org.junit.Test;
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46
/**
57
* @author Chen WeiJie
68
* @date 2020-05-27 17:39:32
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* @Description: zhunn 反转链表2
710
**/
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public class Solution2 {
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4447
return dummy.next;
4548
}
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@Test
51+
public void test() {
52+
ListNode l1_1 = new ListNode(7);
53+
ListNode l1_2 = new ListNode(9);
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ListNode l1_3 = new ListNode(2);
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ListNode l1_4 = new ListNode(10);
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ListNode l1_5 = new ListNode(1);
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ListNode l1_6 = new ListNode(8);
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ListNode l1_7 = new ListNode(6);
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l1_1.next = l1_2;
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l1_2.next = l1_3;
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l1_3.next = l1_4;
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l1_4.next = l1_5;
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l1_5.next = l1_6;
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l1_6.next = l1_7;
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ListNode result = reverseBetween(l1_1,3,6);
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System.out.println(result.val);
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System.out.println(result.next.val);
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System.out.println(result.next.next.val);
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System.out.println(result.next.next.next.val);
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System.out.println(result.next.next.next.next.val);
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System.out.println(result.next.next.next.next.next.val);
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System.out.println(result.next.next.next.next.next.next.val);
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}
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}

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