單鏈表：單指向連結串列

雙向連結串列：前後都指向連結串列

題目1：單鏈表和雙向連結串列如何反轉

package day2;
//反轉連結串列
public class Code01_ReverseList {
	
	public static class Node {
		public int value;
		public Node next;
		public Node(int value,Node next) {
			this.value = value;
			this.next = next;
		}
	}
	
	public static class DoubleNode {
		public int value;
		public DoubleNode last;
		public DoubleNode next;
		
		public DoubleNode(int data) {
			value = data;
		}
	}
	
//	反轉單鏈表
	public static Node reverseLinkedList(Node head) {
		/*
		 *準備一個之前的變數
		 *在準備一個後來的變數
		 *
		 */
		Node pre = null;
		Node next = null;
		while(head != null) {
			next = head.next;
			head.next = pre;
			pre = head;
			head = next;	
		}
		return pre;
	}
	
//	反轉雙向連結串列
	public static DoubleNode reverseDoubleList(DoubleNode head) {
		DoubleNode pre = null;
		DoubleNode next = null;
		while(head != null) {
			next = head.next;
			head.next = pre;
			head.next = next;
			pre = head;
			head = next;
		}
		return pre;	
	}
	
}
 

題目2：把給定值都刪除

package day2;
//刪除連結串列中的一個元素
import day2.Code01_ReverseList.Node;

public class Code02_DeleteGivenValue {
	public static class Node {
		public int value;
		public Node next;
		public Node(int value,Node next) {
			this.value = value;
			this.next = next;
		}
	}
	public static Node removeValue(Node head,int num) {
		while(head != null) {
			if(head.value != num) {
				break;
			}
			head = head.next;
		}
		//head來到第一個不需要刪的位置
		Node pre = head;
		Node cur = head;
		//
		while(cur != null) {
			if(cur.value == num) {
				pre.next = cur.next;	
			} else {
				pre = cur;
			}
			cur = cur.next;
		}	
		return head;
	}
}