LeetCode 题解2：Add Two Numbers

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 0 -> 8

题解

首先想到把这个链表转换成String，在转换成Integer，不过脱离了原题考察链表知识的本意，也忽略了Integer的上限。直接用和链表有关的知识即可，注意细节

代码如下:

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
    
    int carry = 0;
	ListNode tail = new ListNode(0);
	ListNode ptr = tail;
	
	while (l1 != null || l2 != null) {

		int val1 = 0;
		if (l1 != null) {
			val1 = l1.val;
			l1 = l1.next;
		}
		
		int val2 = 0;
		if (l2 != null) {
			val2 = l2.val;
			l2 = l2.next;
		}
		
		
		int temp_sum = val1 + val2 + carry;
		ptr.next = new ListNode(temp_sum % 10);
		carry = temp_sum / 10;
		ptr = ptr.next;
		
	    if(carry == 1)
            ptr.next = new ListNode(1);  
	}
	

	
	return tail.next;

}

Written on January 8, 2016