1. 2_两数相加
/*
输入:(2 -> 4 -> 3) + (5 -> 6 -> 4)
输出:7 -> 0 -> 8
原因:342 + 465 = 807
*/
class Solution {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
if(l1 == null && l2 == null) return null;
else if(l1 == null) return l2;
else if(l2 == null) return l1;
int c = 0;
ListNode ret = new ListNode(-1);
ListNode cur = ret;
while(l1 != null || l2 != null || c != 0)
{
int val1 = (l1 == null) ? 0 : l1.val;
int val2 = (l2 == null) ? 0 : l2.val;
int tmp = val1 + val2 + c;
if(tmp >= 10){
tmp -= 10;
c = 1;
}else {
c = 0;
}
ListNode node = new ListNode(tmp);
cur.next = node;
cur = cur.next;
if(l1 != null) l1 = l1.next;
if(l2 != null) l2 = l2.next;
}
return ret.next;
}
}