解法1 - 递归版本
class Solution {
int flow=0;
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
if(l1==null) return l2;
if(l2==null) return l1;
ListNode res1=l1,res2=l2;
int len1=0,len2=0;
while(l1!=null){
len1++;
l1=l1.next;
}
while(l2!=null){
len2++;
l2=l2.next;
}
ListNode res=len1>len2?add(res1,res2,len1,len2):add(res2,res1,len2,len1);
if(flow==1) {
res1=new ListNode(1);
res1.next=res;
return res1;
}
return res;
}
public ListNode add(ListNode l1, ListNode l2,int len1,int len2) {
int temp;
if((len1==1)&&(len2==1)){
temp=l1.val;
l1.val=(l1.val+l2.val)%10;
flow=(temp+l2.val)/10;
return l1;
}
if(len1>len2) {
temp=l1.val;
l1.next=add(l1.next, l2,len1-1,len2);
l1.val=(temp+flow)%10;
flow=(temp+flow)/10;
return l1;
}
l1.next=add(l1.next, l2.next,len1-1,len2-1);
temp=l1.val;
l1.val=(temp+flow+l2.val)%10;
flow=(temp+flow+l2.val)/10;
return l1;
}
}
解法2 - 非递归版本
class Solution {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
Stack<Integer> stack1=new Stack();
Stack<Integer> stack2=new Stack();
ListNode node1=l1;
while(node1!=null){
stack1.push(node1.val);
node1=node1.next;
}
ListNode node2=l2;
while(node2!=null){
stack2.push(node2.val);
node2=node2.next;
}
ListNode head=null;
int flag=0;
while(!stack1.isEmpty()||!stack2.isEmpty()||flag!=0){
int value=0;
if(!stack1.isEmpty())
value+=stack1.pop();
if(!stack2.isEmpty())
value+=stack2.pop();
value+=flag;
ListNode node=new ListNode(value%10);
flag=value/10;
node.next=head;
head=node;
}
return head;
}
}