[英]Can't print out Add two numbers in Java
我无法从函数AddTwoNumber
返回值main。 我已经检查了函数中的结果,它是正确的。 但是,当我将值从AddTwoNumber
到ListNode start
,它不会显示任何内容。 我认为问题在这里发生:
ListNode dummy = new ListNode(0);
ListNode node = dummy;
但我不知道如何解决。
ListNode.cs:
class ListNode {
public int data; // data stored in this node
public ListNode next; // link to next node in the list
// post: constructs a node with data 0 and null link
public ListNode() {
this(0, null);
}
// post: constructs a node with given data and null link
public ListNode(int data) {
this(data, null);
}
// post: constructs a node with given data and given link
public ListNode(int data, ListNode next) {
this.data = data;
this.next = next;
}
}
Main.cs:
public static void main(String[] args) {
ListNode first = new ListNode(8,
new ListNode(9,
new ListNode(7 )));
ListNode second = new ListNode(3,
new ListNode(5,
new ListNode(6 )));
ListNode start = AddTwoNumber(first,second);
while (start!=null) {
System.out.println(start.next);
start=start.next;
}
}
public static ListNode AddTwoNumber(ListNode first, ListNode second) {
ListNode dummy = new ListNode(0);
ListNode node = dummy;
int Digitsten = 0;
int sum = 0;
//Once fit first&second =null & Digitsten=0,the code can stop
while (first != null || second != null || Digitsten != 0) {
if (first != null && second != null) {
sum += first.data + second.data + Digitsten;
} else if (first!= null) {
sum += first.data + Digitsten;
} else if (second!= null) {
sum += second.data + Digitsten;
} else {
sum=Digitsten; `enter code here`
}
int DigitsOne = sum % 10;
Digitsten = sum / 10;
node = new ListNode(DigitsOne);
node = node.next;
if (first == null) {
first = null;
} else {
first = first.next;
}
if (second == null) {
second = null;
} else {
second = second.next;
}
sum = 0;
}
return dummy.next; //return the value to dummy ListNode
}
真正的问题在您的AddTwoNumber
方法内部。 您不能使节点指向新节点,在移至下一个节点之前,应使其下一个指向新节点。
public static ListNode AddTwoNumber(ListNode first, ListNode second){
ListNode dummy = new ListNode(0);
ListNode node = dummy;
int Digitsten = 0;
int sum = 0;
while (first != null || second != null || Digitsten != 0)
{
if (first != null && second != null)
{
sum += first.data + second.data + Digitsten;
}
else if (first!= null)
{
sum += first.data + Digitsten;
}
else if (second!= null)
{
sum += second.data + Digitsten;
}
else
{
sum=Digitsten; `enter code here`
}
int DigitsOne = sum % 10;
Digitsten = sum / 10;
// LOOK HERE!!!
node.next = new ListNode(DigitsOne);
node = node.next;
if (first == null)
{
first = null;
}
else
first = first.next;
if (second == null)
{
second = null;
}
else
{
second = second.next;
}
sum=0;
}
return dummy.next;//return the value to dummy ListNode
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