用qsort按字母順序組織一個結構

#include <stdio.h> 
#include <string.h> 
#include <stdlib.h> 

#define ARRAY_MAX 100 
#define FNAME 31 
#define LNAME 31 

typedef int (*compfn)(const void*, const void*); 

struct student { 

    char firstName[FNAME]; 
    char lastName[LNAME]; 
    int quiz1, quiz2 , quiz3, quiz4, mid1, mid2, final; 
    char letterGrade; 
    int finalGradePercentage; 
}; 

// Function for Qsort 
int compare(struct student *element1, struct student *element2) 
{ 
    if (element1->firstName[0] < element2->firstName[0]) 
     return -1; 

    else if (element1->firstName[0] > element2->firstName[0]) 
     return 1; 

    else 
     return 0; 
    } 


int main(int argc, char *argv[]){ 


    FILE *inputFile, *outputFile; 
    char buf[100]; 
    char *token; 
    int count = 0; 

    inputFile = fopen("/Users/Home/Desktop/input_data.txt", "r"); 


    struct student studentData[ARRAY_MAX]; 
    while (fgets(buf, sizeof(buf), inputFile) != NULL){ //scan through the input file 
     token = strtok(buf, " "); 
     strcpy(studentData[count].firstName, token); 
     token = strtok(NULL, ","); 
     strcpy(studentData[count].lastName, token); 
     token = strtok(NULL, ","); 
     studentData[count].quiz1 = atoi(token); 
     token = strtok(NULL, ","); 
     studentData[count].quiz2 = atoi(token); 
     token = strtok(NULL, ","); 
     studentData[count].quiz3 = atoi(token); 
     token = strtok(NULL, ","); 
     studentData[count].quiz4 = atoi(token); 
     token = strtok(NULL, ","); 
     studentData[count].mid1 = atoi(token); 
     token = strtok(NULL, ","); 
     studentData[count].mid2 = atoi(token); 
     token = strtok(NULL, ","); 
     studentData[count].final= atoi(token); 


     studentData[count].finalGradePercentage = studentData[count].quiz1 * .10 +studentData[count].quiz2 * .10 + studentData[count].quiz3 * .10 + studentData[count].quiz4 * .10 + studentData[count].mid1 * .20 + studentData[count].mid2 * .15 + studentData[count].final * .25; 

     if (studentData[count].finalGradePercentage <=100 && studentData[count].finalGradePercentage>=90) 
     { 
      studentData[count].letterGrade = 'A'; 
     } 
     else if(studentData[count].finalGradePercentage <= 89 && studentData[count].finalGradePercentage >=80) 
     { 
      studentData[count].letterGrade = 'B'; 
     } 
     else if(studentData[count].finalGradePercentage <= 79 && studentData[count].finalGradePercentage >=70) 
     { 
      studentData[count].letterGrade = 'C'; 
     } 
     else if(studentData[count].finalGradePercentage <= 69 && studentData[count].finalGradePercentage >=60) 
     { 
      studentData[count].letterGrade = 'D'; 
     } 
     else if(studentData[count].finalGradePercentage <= 59){ 
      studentData[count].letterGrade = 'F'; 
     } 


     count++; 
    } 


    qsort((void *) &studentData,count,sizeof(struct student),(compfn)compare);   


    for (int i = 0; i< count; i++) { 
     char name[62]; 

     sprintf(name, "%s %s", studentData[i].firstName, studentData[i].lastName); 
     printf("%-20s %c\n", name, studentData[i].letterGrade); 

    } 

    fclose(inputFile); 
    fclose(outputFile); 

    return 0; 
}

嗨，夥計我很難讓我的結構以字母順序排列。任何幫助這樣做將不勝感激。這是我迄今爲止所擁有的。我認爲問題在於比較功能。但我不確定我真的很瞭解你。任何人都知道一些很好的參考資料來閱讀它。用qsort按字母順序組織一個結構

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2014-11-02 code kid

使用您現有的結構，只比較名字的第一個字符。您需要將字符串與strcmp()進行比較，並且考慮到在班級中可能有兩名學生稱爲約翰或簡，您可能還想在姓氏上進行比較。

int compare(struct student *element1, struct student *element2) 
{ 
    if ((rc = strcmp(element1->firstName, element2->firstName)) != 0) 
     return rc; 
    return strcmp(element1->lastName, element2->lastName); 
}

就整體而言，我更喜歡寫的比較函數爲：

int compare(const void *v1, const void *v2) 
{ 
    const struct student *p1 = (struct student *)v1; 
    const struct student *p2 = (struct student *)v2; 

    if ((rc = strcmp(p1->firstName, p2->firstName)) != 0) 
     return rc; 
    return strcmp(p1->lastName, p2->lastName); 
}

我再沒有給指針轉換爲qsort()因爲指針的功能是相同類型的qsort()的預計。在實踐中，沒有太大的區別。請參閱How to sort an array of structs in C?

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2014-11-02 20:10:01

用qsort按字母順序組織一個結構

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