Add Two Numbers

题目

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

方法

链表的遍历，只需要一遍即可。

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode head=null;
ListNode last = null;
int flag = 0;
while(l1!=null&&l2!=null){
int temp;
temp = l1.val + l2.val + flag;
if (temp >= 10) {
temp = temp - 10;
flag = 1;
} else {
flag = 0;
}

if(head == null){
head = new ListNode(temp);
last = head;
}else{
ListNode cur = new ListNode(temp);
last.next = cur;
last = cur;
}
l1 = l1.next;
l2 = l2.next;
}

while(l1 != null){
if(flag == 1){
int temp = l1.val + 1;
if(temp >= 10){
flag = 1;
temp = temp -10;
}else{
flag = 0;
}

if(head == null){
head = new ListNode(temp);
last = head;
}else{
ListNode cur = new ListNode(temp);
last.next = cur;
last = cur;
}
l1 = l1.next;
}else{
last.next = l1;
break;
}
}
while(l2 != null){
if(flag == 1){
int temp = l2.val + 1;
if(temp >= 10){
flag = 1;
temp = temp -10;
}else{
flag = 0;
}

if(head == null){
head = new ListNode(temp);
last = head;
}else{
ListNode cur = new ListNode(temp);
last.next = cur;
last = cur;
}
l2 = l2.next;
}else{
last.next = l2;
break;
}
}
if(flag == 1){
ListNode lnTemp = new ListNode(1);
last.next = lnTemp;
}
return head;
}