MiddleNode
MiddleNode.java 源码
package datastructure.linkedlist.leetcode;
import java.util.ArrayList;
import java.util.List;
/**
* @author roseduan[roseduan520@gmail.com]
* @time 2019/12/6 0:21
* @description 找到链表的中间节点
*/
public class MiddleNode {
/**
* 使用一个数组
*/
public ListNode findMiddleNode1(ListNode head) {
List<ListNode> list = new ArrayList<>();
while (head != null) {
list.add(head);
head = head.next;
}
return list.get(list.size() / 2);
}
/**
* 计数法，两次遍历
*/
public ListNode findMiddleNode2(ListNode head) {
int count = 0;
ListNode p = head;
while (p != null) {
count++;
p = p.next;
}
count /= 2;
p = head;
while (count-- > 0) {
p = p.next;
}
return p;
}
/**
* 双指针法
*/
public ListNode findMiddleNode3(ListNode head) {
ListNode slow = head, fast = head;
while (fast != null && fast.next != null) {
slow = slow.next;
fast = fast.next.next;
}
return slow;
}
private static class ListNode {
int val;
ListNode next;
ListNode(int val) {
this.val = val;
this.next = null;
}
}
}
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