1 packageofficeCoding;2

3 importjava.util.ArrayList;4 importjava.util.Stack;5

6 /**

7 * 从尾到头遍历链表 输入一个链表，按链表值从尾到头的顺序返回一个ArrayList8 *9 *@authorAdministrator10 */

11 class ListNode {//单链表节点构建

12 intval;13 ListNode next = null;14

15 ListNode(intval) {16 this.val =val;17 }18 }19

20 public classPro_03 {21

22 static ListNode head = null;//创建一个头节点

23

24 public static voidmain(String[] args) {25 addNode(5);26 addNode(8);27 ArrayList list =printListFromTailToHead(head);28 System.out.println(list);29 }30

31 //队列和栈是一对好基友，从尾到头打印链表，当然离不开借助栈的帮忙啦32 //所以，先把链表里的东西，都放到一个栈里去，然后按顺序把栈里的东西pop出来，就这么简单

33 public static ArrayListprintListFromTailToHead(ListNode listNode) {34 Stack stack = new Stack();35 while (listNode != null) {36 stack.push(listNode.val);37 listNode =listNode.next;38 }39 ArrayList list = new ArrayList();40 while (!stack.isEmpty()) {41 list.add(stack.pop());42 }43 returnlist;44 }45

46 //input

47 public static void addNode(intd) {48 ListNode newNode = newListNode(d);49 if (head == null) {50 head =newNode;51 }52 ListNode tmp =head;53 while (tmp.next != null) {54 tmp =tmp.next;55 }56 tmp.next =newNode;57 }58

59 //delete

60 public boolean deleteNode(intindex) {61 if (index < 1 || index >length()) {62 return false;//如果当前index在链表中不存在

63 }64 if (index == 1) {//如果index指定的是头节点

65 head =head.next;66 return true;67 }68 int i = 2;69 ListNode preNode = head;//前一个节点(从头节点开始)

70 ListNode curNode = preNode.next;//当前节点

71 while (curNode != null) {72 if (i ==index) {73 preNode.next = curNode.next;//删除当节点，前节点连接到下节点

74 return true;75 }76 preNode =curNode;77 curNode =curNode.next;78 i++;79 }80 return false;81 }82

83 //返回节点长度

84

85 public intlength() {86 int length = 0;87 ListNode tmp =head;88 while (tmp != null) {89 length++;90 tmp =tmp.next;91 }92 returnlength;93 }94

95 //链表反转

96

97 publicListNode ReverseIteratively(ListNode head) {98 ListNode pReversedHead =head;99 ListNode pNode =head;100 ListNode pPrev = null;101 while (pNode != null) {102 ListNode pNext =pNode.next;103 if (pNext == null) {104 pReversedHead =pNode;105 }106 pNode.next =pPrev;107 pPrev =pNode;108 pNode =pNext;109 }110 this.head =pReversedHead;111 return this.head;112 }113

114 //查找单链表的中间节点

115

116 publicListNode SearchMid(ListNode head) {117 ListNode p = this.head, q = this.head;118 while (p != null && p.next != null && p.next.next != null) {119 p =p.next.next;120 q =q.next;121 }122 System.out.println("Mid:" +q.val);123 returnq;124 }125

126 //查找倒数 第k个元素

127

128 public ListNode findElem(ListNode head, intk) {129 if (k < 1 || k > this.length()) {130 return null;131 }132 ListNode p1 =head;133 ListNode p2 =head;134 for (int i = 0; i < k; i++)//前移k步

135 p1 =p1.next;136 while (p1 != null) {137 p1 =p1.next;138 p2 =p2.next;139 }140 returnp2;141 }142

143 //排序

144

145 publicListNode orderList() {146 ListNode nextNode = null;147 int tmp = 0;148 ListNode curNode =head;149 while (curNode.next != null) {150 nextNode =curNode.next;151 while (nextNode != null) {152 if (curNode.val >nextNode.val) {153 tmp =curNode.val;154 curNode.val =nextNode.val;155 nextNode.val =tmp;156 }157 nextNode =nextNode.next;158 }159 curNode =curNode.next;160 }161 returnhead;162 }163

164 //从尾到头输出单链表，采用递归方式实现

165

166 public voidprintListReversely(ListNode pListHead) {167 if (pListHead != null) {168 printListReversely(pListHead.next);169 System.out.println("printListReversely:" +pListHead.val);170 }171 }172

173 //判断链表是否有环，单向链表有环时，尾节点相同

174

175 public booleanIsLoop(ListNode head) {176 ListNode fast = head, slow =head;177 if (fast == null) {178 return false;179 }180 while (fast != null && fast.next != null) {181 fast =fast.next.next;182 slow =slow.next;183 if (fast ==slow) {184 System.out.println("该链表有环");185 return true;186 }187 }188 return !(fast == null || fast.next == null);189 }190

191 //找出链表环的入口

192

193 publicListNode FindLoopPort(ListNode head) {194 ListNode fast = head, slow =head;195 while (fast != null && fast.next != null) {196 slow =slow.next;197 fast =fast.next.next;198 if (slow ==fast)199 break;200 }201 if (fast == null || fast.next == null)202 return null;203 slow =head;204 while (slow !=fast) {205 slow =slow.next;206 fast =fast.next;207 }208 returnslow;209 }210 }