两数相加

/*
Definition for singly-linked list.
public class ListNode {
int val;
ListNode next;
ListNode(int x) { val = x; }
}
/
class Solution {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode pre = new ListNode(0);
ListNode cur = pre;
int carry = 0;
while(l1 != null || l2 != null) {
int x = l1 == null ? 0 : l1.val;
int y = l2 == null ? 0 : l2.val;
int sum = x + y + carry;

carry = sum / 10;
sum = sum % 10;
cur.next = new ListNode(sum);

        cur = cur.next;<br />            if(l1 != null)<br />                l1 = l1.next;<br />            if(l2 != null)<br />                l2 = l2.next;<br />        }<br />        if(carry == 1) {<br />            cur.next = new ListNode(carry);<br />        }<br />        return pre.next;<br />    }<br />}

作者：guanpengchn
链接：https://leetcode-cn.com/problems/add-two-numbers/solution/hua-jie-suan-fa-2-liang-shu-xiang-jia-by-guanpengc/
来源：力扣（LeetCode）
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

/**

• Definition for singly-linked list.
• public class ListNode {
• int val;
• ListNode next;
• ListNode() {}
• ListNode(int val) { this.val = val; }
• ListNode(int val, ListNode next) { this.val = val; this.next = next; }

• } */ class Solution { public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

   ListNode pre = new ListNode();
   ListNode cru = pre;
   //进位
   int corry = 0;
   while(l1 != null || l2 !=null ){
       int x = l1 == null? 0:l1.val;
       int y = l2 == null? 0:l2.val;
       //注意要加进位
       int sum = x + y + corry;
       corry = sum/10;
       sum = sum%10;
       cru.next = new ListNode(sum);
       cru = cru.next;
       //为空就不能继续下跳
       if(l1!=null){
           l1 = l1.next;
       }
       if(l2!=null){
           l2 = l2.next;
       }
   }
   //如果最后一步还有进位，当然进位最大为1
   if(corry == 1){
       cru.next = new ListNode(corry);
   }
   //注意pre是头节点，而返回要从下一个开始
   return pre.next;

  } }

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode root = new ListNode(0);
        ListNode cursor = root;
        int carry = 0;
        while(l1 != null || l2 != null || carry != 0) {
            int l1Val = l1 != null ? l1.val : 0;
            int l2Val = l2 != null ? l2.val : 0;
            int sumVal = l1Val + l2Val + carry;
            carry = sumVal / 10;
            ListNode sumNode = new ListNode(sumVal % 10);
            cursor.next = sumNode;
            cursor = sumNode;
            if(l1 != null) l1 = l1.next;
            if(l2 != null) l2 = l2.next;
        }
        return root.next;
    }
}