Question

我正在编写一个程序来乘以两个多项式。我需要一些建议，如何在polyProduct函数中的嵌套while循环中重新启动双链表。我的意思是，此时我需要回到列表的第一个位置。这是我到目前为止的代码：

#include "DLListInterface.h"
#include <stdio.h>
#include <stdlib.h>

int numRead(DLnode*,int);
void printList(DLnode*);
DLnode *polyProduct(DLnode*,DLnode*);

int main()
{
    DLnode *number1;
    DLnode *number2;
    DLnode *result;
    int readval;
    int numbterms;
    int i;

    scanf("%d",&numbterms);
    scanf("%d",&readval);

    /* initial DLnode of number1*/
    number1=(DLnode*)malloc(sizeof(DLnode));
    number1->value=readval;
    number1->next=NULL;
    number1->prev=NULL;

    readval=numRead(number1,numbterms);

    scanf("%d",&numbterms);
    scanf("%d",&readval);

    number2=(DLnode*)malloc(sizeof(DLnode));
    number2->value=readval;
    number2->next=NULL;
    number2->prev=NULL;

    readval=numRead(number2,numbterms);

    printf("\n");
    printList(number1);
    printList(number2);
    result=polyProduct(number1,number2);
    printList(result);

    getch();
    return 0;
}

int numRead(DLnode*number,int numbterms)
{
    int readval,i;
    DLnode *anothernode;
    for(i=0;i<(numbterms*2)-1;i++)
    {
        scanf("%d",&readval);
        anothernode=(DLnode*)malloc(sizeof(DLnode));
        anothernode->value=readval;
        anothernode->next=NULL;
        anothernode->prev=Dlast(number);
        Dlast(number)->next=anothernode;
    }
    return readval;
}


DLnode *polyProduct(DLnode*poly1,DLnode*poly2)
{
    DLnode *result;
    DLnode *newnode;
    DLnode *first;
    first=poly2;

    newnode=(DLnode*)malloc(sizeof(DLnode));
    newnode->value=(poly1->value)*(poly2->value);
    newnode->next=NULL;
    newnode->prev=NULL;
    result=newnode;

    poly1=poly1->next;
    poly2=poly2->next;

    newnode=(DLnode*)malloc(sizeof(DLnode));
    newnode->value=poly1->value+poly2->value;
    newnode->next=NULL;
    newnode->prev=Dlast(result);
    Dlast(result)->next=newnode;

    poly1=poly1->prev;
    poly2=poly2->next;


    while(poly1!=NULL)
    {
        while(poly2!=NULL)
        {
            newnode=(DLnode*)malloc(sizeof(DLnode));
            newnode->value=(poly1->value)*(poly2->value);
            newnode->next=NULL;
            newnode->prev=Dlast(result);
            Dlast(result)->next=newnode;

            poly1=poly1->next;
            poly2=poly2->next;

            newnode=(DLnode*)malloc(sizeof(DLnode));
            newnode->value=poly1->value+poly2->value;
            newnode->next=NULL;
            newnode->prev=Dlast(result);
            Dlast(result)->next=newnode;

            poly1=poly1->prev;
            poly2=poly2->next;

        }
        poly1=poly1->next;
        poly2=first; //restart poly 2

    }
    return result;

}


void printList(DLnode*number)
{
    while (number!=NULL)
    {
        printf("%d ",number->value);
        number=number->next;
    }
    printf("\n");
    return;
}

//Declaration of DLnode in DLList.h file
typedef struct Dcontainer
{
    int value;
    struct Dcontainer *next;
    struct Dcontainer *prev;

} DLnode;

Answer 1

进入列表开头的一种方法是操纵指针移动到列表的开头

void seekstart(DLNode* number)
{
     while(number->prev != null)
     {
        number = number->prev;
     }
}

另一个选项是使用临时节点在处理之前存储列表的Starting节点。

DLnode *temp_num1 = number1;
DLnode *temp_num2 = number2;
result=polyProduct(number1,number2);

或者您在节点本身的结构中保留指向根的指针。虽然这可能不是一个有效的解决方案。如果您需要经常访问列表的开头，这非常有用

// DLList.h文件中的DLnode声明

typedef struct Dcontainer
{
int value;
struct Dcontainer *next;
struct Dcontainer *prev;
struct Dcontainer *root;    //root is the starting of the list
} DLnode;

如何重新启动双链表？

1 个答案: