链表系列之单链表——使用单链表实现大整数相加

原文：http://blog.csdn.net/iloveyoujelly/article/details/38321735

大数相加在我之前的一篇博客里有一个使用数组实现的方案，使用单链表实现更灵活。

有两个由单链表表示的数。每个结点代表其中的一位数字。

数字的存储是逆序的， 也就是说个位位于链表的表头。
写一函数使这两个数相加并返回结果，结果也由链表表示。

eg.

 Input:(3->9->6), (4->7->8->3)

Output:(7->6->5->4)

#include <iostream>
#include <stack>
using namespace std;

typedef struct node
{
    int data;
    node *next;
}Node, *LinkList;
//建立链表
Node* createList(const int a[], int n)
{
    Node *head, *endPtr;
    head = endPtr = NULL;

    for(int i=0;i<n;i++)
    {
        Node *temp = new Node; / /node = (struct Node *)malloc(sizeof(struct Node));
        temp->data = a[i];
        temp->next = NULL;

        if(i==0)
        {
            head = endPtr = temp;
        }
        else
        {
            endPtr->next = temp;
            endPtr = temp;
        }
    }

    return head;
}
/*从尾到头打印链表，要求不修改链表结构*/
//使用栈适配器
void PrintListReversing(LinkList pHead)
{
    stack<Node*> nodes;
    Node* pNode = pHead;

    if(pNode==NULL)
        return;

    while(pNode!=NULL)   //将节点依次入栈
    {
        nodes.push(pNode);
        pNode = pNode->next;
    }

    while(!nodes.empty())   //出栈
    {
        pNode = nodes.top();   //读取栈顶元素
        cout<<pNode->data;
        nodes.pop();   //删除栈顶元素
    }
}
//大数相加
Node *ListAdd(Node* L1, Node* L2)
{
    if(L1==NULL)
        return L2;
    if(L2==NULL)
        return L1;

    Node *ptr1 = L1, *ptr2 = L2, *ResultPtr=NULL, *TmpPtr=NULL;
    int carry = 0;

    Node *p_node = new Node();
    p_node->data = (L1->data+L2->data)%10;
    p_node->next = NULL;
    carry = (L1->data+L2->data)/10;
    ResultPtr = TmpPtr = p_node;
    TmpPtr->next = NULL;
    L1 = L1->next;
    L2 = L2->next;

    while(L1 && L2)
    {
        Node *pNode = new Node();
        TmpPtr->next = pNode;

        int tmp = L1->data+L2->data+carry;
        carry = tmp/10;
        pNode->data = tmp%10;
        pNode->next = NULL;

        TmpPtr = TmpPtr->next;
        L1 = L1->next;
        L2 = L2->next;
    }

    while(L1)
    {
        Node *pNode = new Node();
        TmpPtr->next = pNode;

        int tmp = L1->data+carry;
        carry = tmp/10;
        pNode->data = tmp%10;
        pNode->next = NULL;

        TmpPtr = TmpPtr->next;
        L1 = L1->next;
    }
    while(L2)
    {
        Node *pNode = new Node();
        TmpPtr->next = pNode;

        int tmp = L2->data+carry;
        carry = tmp/10;
        pNode->data = tmp%10;
        pNode->next = NULL;

        TmpPtr = TmpPtr->next;
        L2 = L2->next;
    }

    if(carry)
    {
        Node *pNode = new Node();
        TmpPtr->next = pNode;

        pNode->data = carry;
        pNode->next = NULL;
    }

    return ResultPtr;
}

int main()
{
    int a[] = {1,9,9};  //991
    int b[] = {9,8,5,6,6,2,8};   //8266589
    Node *L1 = createList(a,3), *L2 = createList(b,7), *L3 = NULL;

    L3 = ListAdd(L1,L2);

    PrintListReversing(L1);
    cout<<"+";
    PrintListReversing(L2);
    cout<<"=";
    PrintListReversing(L3);
    cout<<endl;

    return 1;
}