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Copy pathAddTwoNumbers.cc
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58 lines (49 loc) · 1.46 KB
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namespace AddTwoNumbers {
class Solution {
public:
ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
if (l1 == NULL && l2 == NULL) {
return NULL;
}
if (l1 == NULL) {
return l2;
}
if (l2 == NULL) {
return l1;
}
ListNode dummy(-1);
ListNode * tail = &dummy;
int carry = 0;
while (l1 != NULL && l2 != NULL) {
int sum = l1->val + l2->val + carry;
carry = sum / 10;
ListNode * cur = new ListNode(sum % 10);
tail->next = cur;
tail = cur;
l1 = l1->next;
l2 = l2->next;
}
ListNode * l = NULL;
if (l1 != NULL) {
l = l1;
} else if (l2 != NULL) {
l = l2;
}
// handle the remaining carry
while (l != NULL) {
int sum = l->val + carry;
carry = sum / 10;
ListNode * cur = new ListNode(sum % 10);
tail->next = cur;
tail = cur;
l = l->next;
}
// handle the last possible new node due to carry
if (carry > 0) {
ListNode * cur = new ListNode(carry);
tail->next = cur;
}
return dummy.next;
}
};
}