Add Two Numbers -- LeetCode

这道题比较简单，是cc150里面的题，思路很明确，就是按照位数读下去，维护当前位和进位，时间复杂度是O(n),空间复杂度是O(1).代码如下： 

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
    int carry = 0;
    int digit = 0;
    ListNode head = null;
    ListNode pre = null;
    while(l1!=null && l2!=null)
    {
        digit = (l1.val+l2.val+carry)%10;
        carry = (l1.val+l2.val+carry)/10;
        ListNode newNode = new ListNode(digit);
        if(head==null)
            head = newNode;
        else
            pre.next = newNode;
        pre = newNode;
        l1 = l1.next;
        l2 = l2.next;
    }
    while(l1!=null)
    {
        digit = (l1.val+carry)%10;
        carry = (l1.val+carry)/10;
        ListNode newNode = new ListNode(digit);
        if(head==null)
            head = newNode;
        else
            pre.next = newNode;
        pre = newNode;
        l1 = l1.next;            
    }
    while(l2!=null)
    {
        digit = (l2.val+carry)%10;
        carry = (l2.val+carry)/10;
        ListNode newNode = new ListNode(digit);
        if(head==null)
            head = newNode;
        else
            pre.next = newNode;
        pre = newNode;
        l2 = l2.next;            
    }        
    if(carry>0)
    {
        ListNode newNode = new ListNode(carry);
        pre.next = newNode;
    }
    return head;
}

Add Two Numbers -- LeetCode,布布扣,bubuko.com

Add Two Numbers -- LeetCode

原文：http://blog.csdn.net/linhuanmars/article/details/19957829