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34 lines (33 loc) · 1.07 KB
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//Leetcode Problem #2 : Add Two Numbers
//Link to problem : https://leetcode.com/problems/add-two-numbers/
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
ListNode * head = new ListNode(-1);
ListNode * tail = head;
int carry = 0; //to calculate carry while adding digits
while (l1 || l2 || carry) {
int n1 = l1 ? l1->val : 0; //Adding zero doesn't change sum
int n2 = l2 ? l2->val : 0;
int sum = n1 + n2 + carry;
carry = sum / 10;
tail->next = new ListNode(sum % 10);
tail = tail->next;
l1 ? l1 = l1->next : NULL;
l2 ? l2 = l2->next : NULL;
}
if (carry)
tail->next = new ListNode(1);
return head->next;
}
};