单链表大整数加法

单链表大整数加法，节点是char型。

First     List:   head->1->8->9

Second List:   head->9->8->1

Result  List:    head->1->1->7->0

实现了单链表（单链表类模板），现在使用单链表实现大整数加法

#include "stdafx.h"
#include "SingleList.h"
#include <string.h>
class BigDataList{
public:
    BigDataList(){
    }
public:
    SingleList<char>* add(SingleList<char> &l1, SingleList<char> &l2);
};
SingleList<char>* BigDataList::add(SingleList<char> &l1 , SingleList<char> &l2){
    l1.ReverseSinglyLinkedList();
    l2.ReverseSinglyLinkedList();
    SingleList<char> *l3=new SingleList<char>;
    int length1 = l1.length();
    int length2 = l2.length();
    int ceil = 0 ;
    int mod = 0;
    int i = 0;
    if(length2==length1){
        for(;i <length1 && i < length2 ; i++){
            mod = ((l1.get(i)-'0')+((l2.get(i)-'0'))+ceil)%10;
            ceil = ((l1.get(i)-'0')+((l2.get(i)-'0'))+ceil)/10;
            l3->insert('0'+mod,i);
        }
        if(ceil>0){
            l3->insert(ceil+'0',i);
        }
    }
    else if(length1>length2){
        for(; i<length2 ; i++){
            mod = ((l1.get(i)-'0')+((l2.get(i)-'0'))+ceil)%10;
            ceil = ((l1.get(i)-'0')+((l2.get(i)-'0'))+ceil)/10;
            l3->insert('0'+mod,i);
        }
        for(;i<length1;i++){
            mod = ((l1.get(i)-'0')+ceil)%10;
            ceil = ((l1.get(i)-'0')+ceil)/10;
            l3->insert('0'+mod,i);
        }
        if(ceil>0){
            l3->insert(ceil+'0',i);
        }
    }
    else{
        for(; i<length1 ; i++){
            mod = ((l1.get(i)-'0')+((l2.get(i)-'0'))+ceil)%10;
            ceil = ((l1.get(i)-'0')+((l2.get(i)-'0'))+ceil)/10;
            l3->insert('0'+mod,i);
        }
        for(;i<length2;i++){
            mod = ((l2.get(i)-'0')+ceil)%10;
            ceil = ((l2.get(i)-'0')+ceil)/10;
            l3->insert('0'+mod,i);
        }
        if(ceil>0){
            l3->insert(ceil+'0',i);
        }
    }
    l3->ReverseSinglyLinkedList();
    l3->print();

    return l3;
}