/* Ch 11 demo: array of records */
#include <stdio.h>
#include <string.h>
#define kNameLength 20

typedef struct 
{
    char name[kNameLength];  /* student name */
    int id;                  /* 5 digit ID */          
    double gpa;              /* grade pt avg */
    char level;              /* F, S, J, or C: class standing */
} student_t;

/* Find the highest of two students based on gpa */
student_t compare_students(const student_t student1,
                   const student_t student2)
{
    if (student1.gpa > student2.gpa)
    {
       return student1;
    }
    else
    {
       return student2;
    }  
}

int main(void)
{
    student_t course[35];  /* list of students in a course */
    student_t highest;     /* higher of two students */
    int count = 1;        /* number of students */
    int one, two;         /* two specific students */
    double diff;          /* difference in gpa's */
    int student;          /* array index */
	     
    scanf("%s", course[1].name);

    /* read student data until sentinel encountered */
    while (strcmp(course[count].name, "quit") != 0)
    {
        scanf("%d %lf %c\n", &course[count].id, &course[count].gpa,  
                             &course[count].level);
        count++;
        scanf("%s", course[count].name);
    }
    count--;

    /* display the list of students */
    for (student = 1; student <= count; student += 1)
    {
         printf("%d %s %d %4.2f %c\n",student, course[student].name,
          course[student].id, course[student].gpa, course[student].level);
    }       
    
    printf("Enter two student numbers: ");
    scanf("%d%d", &one, &two);

    diff = course[one].gpa - course[two].gpa;
    printf("\nThe difference betwwen %s and %s is %4.2f.\n",
             course[one].name, course[two].name, diff);

    highest = compare_students(course[one],course[two]);
    printf("%s is highest.\n", highest.name);
    return 0;
}