leetcode 2. Add 2 numbers knowledge point: 1. listNode check null listNode dummy node traverse using node=node.next 2. Add number: res =sum%10 carry=sum/10 public ListNode addTwoNumbers(ListNode l1, ListNode l2) { if(l1==null) return l2; if(l2==null) return l1; ListNode dummy=new ListNode(0); ListNode res=dummy; int sum=0; while(l1!=null || l2!=null){ if(l1!=null){ sum+=l1.val; l1=l1.next; } if(l2!=null){ sum+=l2.val; l2=l2.next; } res.next=new ListNode(sum%10); res=res.next; sum=sum/10; } if(sum>0) res.next=new ListNode(sum); return dummy.next; } |