This is my CPP solution.
class Solution {
private:
int lenCount(ListNode* head){
int n = 0;
ListNode* temp = head;
while(temp){
n++;
temp = temp->next;
}
return n;
}
public:
ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
int n1 = lenCount(l1), n2 = lenCount(l2);
if(n1<n2){
ListNode* temp = l1;
l1 = l2;
l2 = temp;
}
ListNode *res = l1;
int carry = 0;
while(l2!=NULL){
int sum = l2->val + l1->val + carry;
l1->val = sum%10;
carry = sum/10;
l2 = l2->next;
if(l1->next==NULL && carry){
ListNode* newNode = new ListNode();
newNode->val = carry;
newNode->next = NULL;
l1->next = newNode;
return res;
}
l1 = l1->next;
}
while(l1!=NULL){
int sum = l1->val + carry;
l1->val = sum%10;
carry = sum/10;
if(l1->next==NULL && carry){
ListNode* newNode = new ListNode;
newNode->val = carry;
newNode->next = NULL;
l1->next = newNode;
return res;
}
l1 = l1->next;
}
return res;
}
};