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addTwoNums.cpp
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addTwoNums.cpp
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/**
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
*/
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
#include <iostream>
#include <stdlib.h>
using std::cout;
using std::endl;
struct ListNode{
int val;
ListNode* next;
ListNode(int x) : val(x), next(NULL) {}
};
class Solution {
public:
ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
//create mark for the two linked lists
ListNode* mark1 = l1;
ListNode* mark2 = l2;
ListNode* result;
ListNode* resultPivit;
//the carry
int carry = 0;
//this position result
int thisRe = 0;
if(l1 == NULL){
return l2;
} else if(l2 == NULL){
return l1;
} else{
//calculate the first digit
thisRe = mark1 -> val + mark2 -> val;
if(thisRe > 9){
carry = thisRe/10;
thisRe = thisRe % 10;
}
ListNode* thisNode = new ListNode(thisRe);
result = thisNode;
resultPivit = result;
mark1 = mark1 -> next;
mark2 = mark2 -> next;
//calculate the same position in both l1 and l2
while(mark1 != NULL && mark2 != NULL){
thisRe = mark1 -> val + mark2 -> val + carry;
carry = thisRe/10;
thisRe = thisRe % 10;
ListNode* thisNode = new ListNode(thisRe);
resultPivit -> next = thisNode;
resultPivit = resultPivit -> next;
mark1 = mark1 -> next;
mark2 = mark2 -> next;
}
//if l1 and l2 are same in length
if(mark2 == NULL && mark1 == NULL){
if(carry == 0){
return result;
} else{
ListNode* thisNode = new ListNode(carry);
resultPivit -> next = thisNode;
return result;
}
} else if(mark2 == NULL){ //l1 is longer
while(mark1 != NULL && carry != 0){
thisRe = mark1 -> val + carry;
carry = thisRe/10;
thisRe = thisRe % 10;
ListNode* thisNode = new ListNode(thisRe);
resultPivit -> next = thisNode;
resultPivit = resultPivit -> next;
mark1 = mark1 -> next;
}
if(carry != 0){
ListNode* thisNode = new ListNode(carry);
resultPivit -> next = thisNode;
} else{
resultPivit -> next = mark1;
}
return result;
} else{ //l2 is longer
while(mark2 != NULL && carry != 0){
thisRe = mark2 -> val + carry;
carry = thisRe/10;
thisRe = thisRe % 10;
ListNode* thisNode = new ListNode(thisRe);
resultPivit -> next = thisNode;
resultPivit = resultPivit -> next;
mark2 = mark2 -> next;
}
if(carry != 0){
ListNode* thisNode = new ListNode(carry);
resultPivit -> next = thisNode;
} else{
resultPivit -> next = mark2;
}
return result;
}
}
}
void printList(ListNode* head){
ListNode* mark = head;
while(mark != NULL){
cout << mark -> val;
mark = mark -> next;
}
cout << endl;
}
};
int main(int argc, char const *argv[])
{
Solution test;
//test case
//the first digit
ListNode* first = new ListNode(2);
ListNode* second = new ListNode(4);
ListNode* third = new ListNode(3);
first -> next = second;
second -> next = third;
//the second digit
ListNode* firstt = new ListNode(9);
ListNode* secondt = new ListNode(6);
ListNode* thirdt = new ListNode(9);
firstt -> next = secondt;
secondt -> next = thirdt;
ListNode* result = test.addTwoNumbers(first, firstt);
test.printList(first);
test.printList(firstt);
test.printList(result);
return 0;
}