package linkedlist;
/**
 * 單雙鏈表的操作都一樣，需要額外兩個變量：pre和curNext
 * 每次先更新curNext保存好下一個元素的指針，然后進行翻轉(zhuǎn)更新，最后再將pre更新
 * */
public class ReverseList {

class Node {
    int value;
    Node next;
    Node(int value){
        this.value = value;
    }
}
public static Node reverseSingle(Node listA) {
    if(listA == null) {
        return null;
    }
    Node pre = null;
    Node curNext = null;

    while (listA!=null) {
        curNext = listA.next;
        listA.next = pre;
        pre = listA;
        listA = curNext;
    }
    return pre;
}

class DoubleNode {
    int value;
    DoubleNode next;
    DoubleNode last;
    DoubleNode(int value){
        this.value = value;
    }
}
public static DoubleNode reverseDoule(DoubleNode head) {
    if(head ==null)
        return null;
    DoubleNode pre = null;
    DoubleNode curNext = null;
    while(head!=null) {
        curNext = head.next;
        head.next = pre;
        head.last = curNext;
        pre = head;
        head = curNext;
    }

    return pre;

}    
}