Question

我正在编写一个从txt文件中读取的程序，并将内容添加到链表中。然后，通过命令提示符中的用户界面，我应该能够查看列表，从列表中添加/删除，并使用部件号搜索列表中的项目以查看其完整详细信息。

目前我遇到两个问题：

1.在主函数的switch case 1中，我插入一个节点，tempNODE-＆gt; item.dataitem = getInfo（）; line在while循环之外正常工作，但是当我把它放在while循环中时，它会跳过新项目的名称并直接转到部件号。我无法弄清楚为什么会这样做。

2.在主函数的切换案例3中，我无法弄清楚如何打印搜索节点的内容，由于NODE结构内部的联合，DisplayNode函数将无法工作（我想要找出如何在不改变NODE结构的情况下打印它。）

这是我目前的代码：

#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>

typedef struct inventory
{
    char invName[36];
    int  invPartNo;
    int  invQOH;
    float invUnitCost;
    float invPrice;
}stock;

struct  NODE
{
    union
    {
        int  nodeCounter;
        void  *dataitem;
    }item;
    struct NODE *link;
};

struct NODE *InitList();
void DisplayNode(struct inventory *);
struct inventory * ReadData(FILE *);
void DisplayList(struct NODE *);
struct NODE* GetNode(FILE *);
void  Add2List(struct NODE *, struct NODE *);
struct NODE* SearchList(struct NODE *, int );
void  DeleteNode(struct NODE *, int );
void readFromText(FILE *, struct NODE *);
struct inventory *getInfo();

int main(int argc, char* argv[])
{
    //create new linked list
    struct NODE *header;
    header = InitList();

    //open text file and read all inputs into the linked list
    FILE *fp = fopen("input.txt", "r");
    readFromText(fp, header);

    //divider
    printf("\n--------------------------------------------------\n\n");

    int input = 0;
    int a = 0;
    struct NODE *tempNODE = (struct NODE*)malloc(sizeof NODE);
    //tempNODE->item.dataitem = getInfo(); //lets user input info from cmd
    //Add2List(header, tempNODE); //inserts the new node into the list

    while(a == 0)
    {
        printf("\n\nEnter a number to select an option: \n");
        printf("1 Insert item \n");
        printf("2 Delete item \n");
        printf("3 Look up item \n");
        printf("4 Print current list of items \n");
        printf("5 Exit \n");

        scanf("%d", &input);
        switch(input)
        {
        case 1:
            //insert a node (Add2List function)
            tempNODE->item.dataitem = getInfo(); //lets user input info from cmd
            Add2List(header, tempNODE); //inserts the new node into the list

        break;

        case 2:
            printf("Enter item number to delete \n");
            int iNumber;
            scanf("%d", &iNumber);
            DeleteNode(header, iNumber);
            printf("Item %d deleted", iNumber);
        break;

        case 3:
            printf("Enter item number to search \n");
            int searchNumber;
            scanf("%d", &searchNumber);
            //create temp node to take value from search
            //struct NODE *tempNODE = (struct NODE*)malloc(sizeof NODE);
            tempNODE = SearchList(header, searchNumber); //returns a node
            //display node contents
            //DisplayNode(tempNODE->item);
        break;

        case 4:
            DisplayList(header);
        break;

        case 5:
            a = 1; //ends the while loop
        break;

        default:
            a = 1; //ends the while loop
        }

    }

    //divider
    printf("\n--------------------------------------------------\n\n");

    return 0;
}

struct NODE *InitList()
{
    struct NODE *temp = (struct NODE*)malloc(sizeof NODE);

    temp->item.nodeCounter = 0;
    temp->link = NULL;
    return temp;
}


void  Add2List(struct NODE *start, struct NODE *NewNode)
{
    struct NODE *current = start;

    while (current->link != NULL)
        current = current->link;

    current->link = NewNode;
    NewNode->link = NULL;

    start->item.nodeCounter++;
}


struct NODE* GetNode(FILE *fptr)
{
    struct NODE *temp = (struct NODE*)malloc(sizeof NODE);

    temp->item.dataitem = ReadData(fptr);
    temp->link = NULL;

    return temp;
}


void DisplayList(struct NODE *start)
{
    struct NODE *current = start->link;

    while (current != NULL)
    {
        DisplayNode((struct inventory *)current->item.dataitem);
        current = current->link;

    }
}


void DisplayNode(struct inventory *stuff)
{
    printf("Name: %s\n", stuff->invName);
    printf("Part Number: %.5d\n", stuff->invPartNo);//printf(“ %.9d”, x)
    printf("Quantity on hand: %d\n", stuff->invQOH);
    printf("Unit Cost: %0.2f\n", stuff->invUnitCost);
    printf("Price %0.2f\n\n", stuff->invPrice);
}


struct inventory * ReadData(FILE *fptr)
{
    struct inventory *temp = (struct inventory *)malloc(sizeof inventory);

    if(fptr==stdin)
        printf("Enter item name: ");
    fscanf_s(fptr, "%s", temp->invName);
    if(fptr==stdin)
        printf("Enter item part number: ");
    fscanf_s(fptr, "%d", &temp->invPartNo);
    if(fptr==stdin)
        printf("Enter item quantity on hand: ");
    fscanf_s(fptr, "%d", &temp->invQOH);
    if(fptr==stdin)
        printf("Enter item unit cost: ");
    fscanf_s(fptr, "%f", &temp->invUnitCost);
    if(fptr==stdin)
        printf("Enter item price: ");
    fscanf_s(fptr, "%f", &temp->invPrice);

    return temp;
}

struct NODE* SearchList(struct NODE *start, int oldData)
{
    struct NODE* current = start;
    struct inventory * st = (struct inventory *)current->link->item.dataitem;

    while (st->invPartNo != oldData && current != NULL)
    {
        current = current->link;
        if(current->link)
            st = (struct inventory *)current->link->item.dataitem;
    }
    return current;
}

void  DeleteNode(struct NODE *start, int oldData)
{
    struct NODE *current, *oldNode;

    current = SearchList( start, oldData);
    oldNode = current->link;
    current->link = oldNode->link;
    free(oldNode);
    start->item.nodeCounter -= 1;
}

void readFromText(FILE *fp, struct NODE *header)
{
    if( fp != NULL )
    {
        while(!feof(fp))
        {
            struct NODE *nNode =  (struct NODE*)malloc(sizeof NODE);
            struct inventory *newNode =  (struct inventory*)malloc(sizeof inventory);

            fgets(newNode->invName, 100, fp);
            fscanf(fp, " %d %d %f %f ", &newNode->invPartNo,&newNode->invQOH,&newNode->invUnitCost,&newNode->invPrice);
            nNode->item.dataitem = newNode;
            header->item.nodeCounter++;
            Add2List(header, nNode);
        }
     }
}

struct inventory *getInfo()
{
    struct inventory *temp =  (struct inventory*)malloc(sizeof inventory);

    printf("Enter item name: ");
    scanf("%99[^\n]", temp->invName); //scans whole line up to 99 characters or until \n

    printf("Enter item part number: ");
    scanf("%d", &temp->invPartNo);

    printf("Enter item quantity on hand: ");
    scanf("%d", &temp->invQOH);

    printf("Enter item unit cost: ");
    scanf("%f", &temp->invUnitCost);

    printf("Enter item price: ");
    scanf("%f", &temp->invPrice);

    return temp;
}

这是我读到的文本文件：

#1 Flat Blade Screwdriver
12489
36
.65
1.75
#2 Flat Blade Screwdriver
12488
24
.70
1.85
#1 Phillips Screwdriver
12456
27
0.67
1.80
#2 Phillips Screwdriver
12455
17
0.81
2.00
Claw Hammer
03448
14
3.27
4.89
Tack Hammer
03442
9
3.55
5.27
Cross Cut Saw
07224
6
6.97
8.25
Rip Saw
07228
5
6.48
7.99
6" Adjustable Wrench
06526
11
3.21
4.50

Answer 1

1.在主函数的switch case 1中，我插入一个节点，tempNODE-＆gt; item.dataitem = getInfo（）;线以外正常工作 while循环，但是当我把它放在while循环中时，它会跳过取新项目的名称并直接转到部件号。我无法弄清楚为什么会这样做。

这是因为您在第241行传递给scanf（）的格式字符串未指定读取任何内容。也就是说，你有这个：

scanf("%99[^\n]", temp->invName); //scans whole line up to 99 characters or until \n

应该是这样的：

scanf("%99s[^\n]", temp->invName); //scans whole line up to 99 characters or until \n

2.在主函数的切换案例3中，我无法弄清楚如何打印搜索节点的内容，DisplayNode函数由于NODE结构内部的联合，我不会对它起作用（I 我想弄清楚如何在不改变结构的情况下打印它节点）。

好吧，你可以打印出这样的联盟：

printf("tempNODE->item.nodeCounter=%i\n", tempNODE->item.nodeCounter);
printf("tempNODE->item.dataitem=%p\n", tempNODE->item.dataitem);

当然注意，这两个打印行中的一个将显示任何特定节点的错误/不相关信息，因为联合一次只能是其组成成员之一 - 例如，如果特定节点已设置保存nodeCounter（整数）值，然后你不应该真正访问第二行中的dataitem成员值，或者如果节点已被设置为保存数据项（指针）值，那么你不应该访问nodeCounter成员变量。所以你应该有办法知道这两个工会成员中哪一个是有效的，哪个不是。典型的方法是将一个单独的成员添加到您设置的结构（在联合之外）以指示联合设置的内容 - 这称为标记联合。但如果你不这样做，你将不得不提出一些其他的机制。

C链接列表打印

1 个答案: