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Code01_LinkedListMid.java
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package class09;
import java.util.ArrayList;
public class Code01_LinkedListMid {
public static class Node {
public int value;
public Node next;
public Node(int v) {
value = v;
}
}
// head 头
public static Node midOrUpMidNode(Node head) {
if (head == null || head.next == null || head.next.next == null) {
return head;
}
// 链表有3个点或以上
Node slow = head.next;
Node fast = head.next.next;
while (fast.next != null && fast.next.next != null) {
slow = slow.next;
fast = fast.next.next;
}
return slow;
}
public static Node midOrDownMidNode(Node head) {
if (head == null || head.next == null) {
return head;
}
Node slow = head.next;
Node fast = head.next;
while (fast.next != null && fast.next.next != null) {
slow = slow.next;
fast = fast.next.next;
}
return slow;
}
public static Node midOrUpMidPreNode(Node head) {
if (head == null || head.next == null || head.next.next == null) {
return null;
}
Node slow = head;
Node fast = head.next.next;
while (fast.next != null && fast.next.next != null) {
slow = slow.next;
fast = fast.next.next;
}
return slow;
}
public static Node midOrDownMidPreNode(Node head) {
if (head == null || head.next == null) {
return null;
}
if (head.next.next == null) {
return head;
}
Node slow = head;
Node fast = head.next;
while (fast.next != null && fast.next.next != null) {
slow = slow.next;
fast = fast.next.next;
}
return slow;
}
public static Node right1(Node head) {
if (head == null) {
return null;
}
Node cur = head;
ArrayList<Node> arr = new ArrayList<>();
while (cur != null) {
arr.add(cur);
cur = cur.next;
}
return arr.get((arr.size() - 1) / 2);
}
public static Node right2(Node head) {
if (head == null) {
return null;
}
Node cur = head;
ArrayList<Node> arr = new ArrayList<>();
while (cur != null) {
arr.add(cur);
cur = cur.next;
}
return arr.get(arr.size() / 2);
}
public static Node right3(Node head) {
if (head == null || head.next == null || head.next.next == null) {
return null;
}
Node cur = head;
ArrayList<Node> arr = new ArrayList<>();
while (cur != null) {
arr.add(cur);
cur = cur.next;
}
return arr.get((arr.size() - 3) / 2);
}
public static Node right4(Node head) {
if (head == null || head.next == null) {
return null;
}
Node cur = head;
ArrayList<Node> arr = new ArrayList<>();
while (cur != null) {
arr.add(cur);
cur = cur.next;
}
return arr.get((arr.size() - 2) / 2);
}
public static void main(String[] args) {
Node test = null;
test = new Node(0);
test.next = new Node(1);
test.next.next = new Node(2);
test.next.next.next = new Node(3);
test.next.next.next.next = new Node(4);
test.next.next.next.next.next = new Node(5);
test.next.next.next.next.next.next = new Node(6);
test.next.next.next.next.next.next.next = new Node(7);
test.next.next.next.next.next.next.next.next = new Node(8);
Node ans1 = null;
Node ans2 = null;
ans1 = midOrUpMidNode(test);
ans2 = right1(test);
System.out.println(ans1 != null ? ans1.value : "无");
System.out.println(ans2 != null ? ans2.value : "无");
ans1 = midOrDownMidNode(test);
ans2 = right2(test);
System.out.println(ans1 != null ? ans1.value : "无");
System.out.println(ans2 != null ? ans2.value : "无");
ans1 = midOrUpMidPreNode(test);
ans2 = right3(test);
System.out.println(ans1 != null ? ans1.value : "无");
System.out.println(ans2 != null ? ans2.value : "无");
ans1 = midOrDownMidPreNode(test);
ans2 = right4(test);
System.out.println(ans1 != null ? ans1.value : "无");
System.out.println(ans2 != null ? ans2.value : "无");
}
}