add two numbers
You are given two non-empty linked lists representing two non-negative integers. Each of their digits is stored in reverse order, and each node can only store one digit.
Please add two numbers and return a linked list representing the sum in the same form.
You can assume that neither number starts with a zero other than the number zero.
Example 1:
Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [7,0,8]
Explanation: 342 + 465 = 807.
Example 2:
Input: l1 = [0], l2 = [0]
Output: [0]
Example 3:
Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
Output: [8,9,9,9,0,0,0,1]
hint:
The number of nodes in each linked list is in the range [1, 100]
0 <= Node.val <= 9
Title data guarantee that the number represented by the list does not contain leading zeros
answer:
Solution one:
class Solution {
public ListNode addTwoNumbers(ListNode listNode1, ListNode listNode2) {
ListNode head = null;
ListNode tail = null;
int carry = 0;
while(listNode1 != null || listNode2 != null) {
int n1 = listNode1 != null ? listNode1.val : 0;
int n2 = listNode2 != null ? listNode2.val : 0;
int sum = n1 + n2 + carry;
if (head == null) {
ListNode pre = new ListNode(sum % 10);
head = tail = pre;
} else {
tail.next = new ListNode(sum % 10);
tail = tail.next;
}
carry = sum / 10;
if(listNode1 != null) {
listNode1 = listNode1.next;
}
if(listNode2 != null) {
listNode2 = listNode2.next;
}
}
if(carry > 0) {
tail.next = new ListNode(carry);
}
return head;
}
}
Solution two:
class Solution {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode node = new ListNode(0);
ListNode preNode = node;
int carry = 0;
int sum = 0;
while(l1 !=null || l2 != null || carry != 0) {
sum = carry;
if(l1 != null) {
sum = sum + l1.val;
l1 = l1.next;
}
if(l2 != null) {
sum = sum + l2.val;
l2 = l2.next;
}
ListNode node1 = new ListNode(sum % 10);
preNode.next = node1;
preNode = preNode.next;
carry = sum / 10;
}
return node.next;
}
}
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