將鏈表作為參數傳遞給 C 中的函數

Question

我正在編寫一個創建鏈接列表的程序。 列表的每個節點存儲 4 個關於患者的數據。 這部分有效。 在用戶決定輸出所有數據后。 將計算數據庫中人的平均身高。 我可以在主函數中執行此操作，但我無法使用外部函數void avr_height(LIST_HEAD *InpList) 。

我的問題是我在這里做錯了什么？ 我懷疑，由於我對指針的理解有限，我在遍歷外部函數中的列表時搞砸了一些事情。 或者錯誤地將列表傳遞給外部函數。

那是在主函數中計算平均值的部分

    pTemp = DataBase.pFirst_elmt;

    while(pTemp != NULL)
    {
        iCurrent = pTemp->Patient.iHeight;
        iSum = iSum + iCurrent;
        pTemp = pTemp->next;
        iNumb++;
    }

    fAvrageH = ((float)iSum) / ((float)iNumb);
    printf("\n\nThe average height of these patients is: %.2f\n\n", fAvrageH);

這是我的外部功能，應該做同樣的事情。

void avr_height(LIST_HEAD *InpList)
{
    int iNumb = 0;
    int iSum = 0;
    int iCurrent = 0;
    float fAvrageH = 0;

    NODE *pTemp = NULL;
    pTemp = InpList;

    while(pTemp != NULL)
    {
        iCurrent = pTemp->Patient.iHeight;
        iSum = iSum + iCurrent;
        pTemp = pTemp->next;
        iNumb++;
    }

    fAvrageH = ((float)iSum) / ((float)iNumb);

    printf("The average height of these patients is: %f", fAvrageH);
}

對於函數void avr_height(LIST_HEAD *InpList)我傳遞了一個struct LIST_HEAD Database作為參數。 這是通過調用avr_height(&DataBase)完成的

所有代碼如下所示：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define STRSIZE 80

//List element's data
typedef struct{
    int iID;
    int iAge;
    int iHeight;

    //Defining a character array for storing the name
    char sName[STRSIZE];

} PATIENT;



//Defining the list elements (German: KNOTEN)
typedef struct NODE{

    //Initialising a Patient of the data type PATIENT. Then pointing to the next element
    PATIENT Patient;
    struct NODE *next;
} NODE;



//Defining the list element's head
typedef struct{

    NODE *pFirst_elmt;
    int iNumber;
}LIST_HEAD;



//Function for creating the actual list
void add_patient(LIST_HEAD *List)
{
    //Allocating memory for list elements
    NODE *pTemp;
    pTemp = (NODE*) malloc(sizeof(NODE));

    //Creating new elements of the linked list (and checking input validity)
    printf("\nEnter patient ID:");
    if(scanf("%d", &pTemp->Patient.iID) == 0){
        printf("Invalid input...");
    }

    printf("Enter patient's name:");
    if(scanf("%s", pTemp->Patient.sName) == 0){
        printf("Invalid input...");
    }

    printf("Enter patient age:");
    if(scanf("%d", &pTemp->Patient.iAge) == 0){
        printf("Invalid input...");
    }

    printf("Enter patient height:");
    if(scanf("%d", &pTemp->Patient.iHeight) == 0){
        printf("Invalid input...");
    }

    //Setting the first element of the list AS the the next element, in front of the new element
    pTemp -> next = List -> pFirst_elmt;
    //Designating the new element of the list as the first element of the list. Increase the number of elements in the list
    List -> pFirst_elmt = pTemp;
    List -> iNumber++;

    printf("\n");
}



//Calculating the average height of the patients: i.e. ITTERATING OVER A LINKED LIST
void avr_height(LIST_HEAD *InpList)
{
    int iNumb = 0;
    int iSum = 0;
    int iCurrent = 0;
    float fAvrageH = 0;

    NODE *pTemp = NULL;
    pTemp = InpList;

    while(pTemp != NULL)
    {
        iCurrent = pTemp->Patient.iHeight;
        iSum = iSum + iCurrent;
        pTemp = pTemp->next;
        iNumb++;
    }

    fAvrageH = ((float)iSum) / ((float)iNumb);

    printf("The average height of these patients is: %f", fAvrageH);
}



int main()
{
    //Variable initialisation
    int i = 0;
    LIST_HEAD DataBase;
    DataBase.pFirst_elmt = NULL;
    DataBase.iNumber = 0;
    NODE *pTemp = NULL;

    //Variables for the height calculation
    int iNumb = 0;
    int iSum = 0;
    int iCurrent = 0;
    float fAvrageH = 0;

    //Loop for creating list elements if specified by user:
    do
    {
        printf("[0] Output the stored data [1] Enter data\n");
        printf("What do you wish to do?\n");

        //Checking input validity
        if(scanf("%i", &i) == 0){
            printf("\nInvalid input...");
        }

        if(i == 1){
            add_patient(&DataBase);
        }

    } while(i);

    pTemp = DataBase.pFirst_elmt;
    printf("\n\n");


    //Outputting the linked list: i.e. ITTERATING OVER A LINKED LIST
    while(pTemp != NULL)
    {
        printf("\nPatient ID: %d  Patient name: %s  Patient age: %d  Patient height: %d", pTemp->Patient.iID, pTemp->Patient.sName, pTemp->Patient.iAge, pTemp->Patient.iHeight);
        pTemp = pTemp->next;
    }


    //Calculating the average height
    pTemp = DataBase.pFirst_elmt;

    while(pTemp != NULL)
    {
        iCurrent = pTemp->Patient.iHeight;
        iSum = iSum + iCurrent;
        pTemp = pTemp->next;
        iNumb++;
    }

    fAvrageH = ((float)iSum) / ((float)iNumb);
    printf("\n\nThe average height of these patients is: %.2f\n\n", fAvrageH);

    //Alternative way of calculating the height with a linked list
    avr_height(&DataBase);

    printf("\n\n");

    return 0;
}

感謝所有幫助，在此先感謝！

Answer 1

編譯器應該為函數發出一條消息

void avr_height(LIST_HEAD *InpList)
{
    int iNumb = 0;
    int iSum = 0;
    int iCurrent = 0;
    float fAvrageH = 0;

    NODE *pTemp = NULL;
    pTemp = InpList;
    //...

因為指針 pTemp 和 InpList 具有不同的類型。

你需要寫

pTemp = InpList->pFirst_elmt;

這個變量也是多余的

int iNumb = 0;

因為列表已經有數據成員int iNumber; .