导读
本文主体为单项链表和双向链表的反转以及简单的测试，以便于理解链表相关的算法题目。
链表
特点
- 便于增删数据，不便于寻址
- 在内存中属于跳转结构
单链表和双链表的定义
单链表： 值，一条next指针
双链表：值，一条last指针，一条next指针
单向链表
Node结点
public static class Node {
public int value;
public Node next;
public Node(int value) {
this.value = value;
}
@Override
public String toString() {
ArrayList<Integer> nums = new ArrayList<>();
Node node = this;
while (node != null) {
nums.add(node.value);
node = node.next;
}
return nums.toString();
}
}反转单向链表
public static Node reverseLinkedList(Node head) {
Node next = null;
Node pre = null;
while (head != null) {
next = head.next;
head.next = pre;
pre = head;
head = next;
}
return pre;
}
测试函数
public static void main(String[] args) {
Node node = new Node(1);
node.next = new Node(2);
node.next.next = new Node(3);
node = reverseLinkedList(node);
System.out.println(node);
}
输出结果如下：
[3, 2, 1]
双向链表
Node结点
public static class DoubleList {
public int value;
public DoubleList next;
public DoubleList last;
public DoubleList(int value) {
this.value = value;
}
@Override
public String toString() {
ArrayList<Integer> nums = new ArrayList<>();
DoubleList node = this;
while (node != null) {
nums.add(node.value);
node = node.next;
}
return nums.toString();
}
}反转双向链表
public static DoubleList reverseDoubleList(DoubleList head) {
DoubleList next;
DoubleList pre = null;
while (head != null) {
next = head.next;
head.next = pre;
// 注意和单项链表不一样的地方只有这一行，其他都基本一样
head.last = next;
pre = head;
head = next;
}
return pre;
}
测试代码
public static void main(String[] args) {
DoubleList node1 = new DoubleList(1);
node1.next = new DoubleList(2);
node1.next.last = node1;
node1.next.next = new DoubleList(3);
node1.next.next.last = node1.next;
System.out.println("reverseDoubleList(node1) = " + reverseDoubleList(node1));
}
输出结果如下：
reverseDoubleList(node1) = [3, 2, 1]
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