I'm currently trying to write a program for a student database assignment. After manually setting 3 elements of the structure array, the next 3 students' details are inputted by the user.
I am trying to write a function that finds the oldest age of the 6 students and returns it as a student_t entry at index max. I'm struggling with how to actually give the function the pointer that is pointing to the first element of the array stdt[6] and then using the pointer within the function. I also have no idea how I would go about returning to main the entry that has the highest age. If I'm trying to say that the value of an element of array of structures is equal to some other integer (max), doesn't that mean that max is now some other block of memory with an integer value and not linked to the array? So I'm not sure how I would return the entry that has the highest age after the function determines the max age.
This is all I've written so far:
#include <stdlib.h>
#include <stdio.h>
typedef struct {
char *name;
char *surname;
char *UUN;
char *department;
char gender;
int age;
}student_t;
student_t findOldest(student_t *studentarr, int len){
int i;
int x;
int max;
max=0;
for(i=0;i<len;i++){
(p+i).age=x;
if(x>max){
x=max;
}
}
}
int main() {
int i;
student_t stdt[6]={{"John","Bishop","s1234","Inf",'m',18},{"Lady","Cook","s2345","Eng",'f',21},{"James","Jackson","s33456","Eng",'m',17}};
student_t *p=&stdt[0];
for(i=3;i<6;i++) {
printf("First name: \n");
scanf("%s",stdt[i].name);
printf("Last name: \n");
scanf("%s",stdt[i].surname);
printf("UUN: \n");
scanf("%s",stdt[i].UUN);
printf("Department: \n");
scanf("%s",stdt[i].department);
printf("Gender (m/f): \n");
scanf("%c",stdt[i].gender);
printf("Age: \n");
scanf("%d",stdt[i].age);
}
findOldest(p,6);
return 0;
}
This should work.
student_t findOldest(student_t *p, int len){
int i;
student_t max = *(p+0);
for(i=1;i<len;i++)
{if((*(p+i)).age > max.age)
max = *(p+i);
}
return max;
}
You want to return the student so keep the student in your max variable not the age. And to refer to pointers either use
(p+i)->age > max.age
or use
(*(p+i)).age > max.age
But there are other problems with the code.
Related
struct student{
char firstname[100];
char lastname[100];
int age;
float credit;
}s[2];
int main() {
int i,j;
printf("Students information\n");
// program that allocates the information
for(i=0;i<2;i++){
printf("Enter full name:");
scanf("%s",s[i].firstname);// scans the name
scanf("%s",s[i].lastname);// scans the name
printf("Age:");
scanf("%d",&s[i].age); // scans the age
printf("Credit:");
scanf("%f",&s[i].credit);
}
// sorting in order of ages
int rep,temp,res;
char name1[100], lname[100];
float cred;
for(i=0;i<2;i++){
for(j=1;j<2;j++){
if(s[i].age < s[j].age){
temp=s[i].age;
s[i].age=s[j].age;
s[j].age= temp;
cred=s[i].credit;
s[i].credit=s[j].credit;
s[j].credit=cred;
}
}
}
// displaying stored information
printf("Name\t\t\tAge\t\t\tCredits Earned\n");
for(i=0;i<2;i++){
printf("%s %s\t\t",s[i].firstname, s[i].lastname);
printf("%d\t\t%.2f",s[i].age, s[i].credit);
printf("\n");
}
return 0;
}
I am trying to sort the first and last name in alphabetical order. While I have figured out how to change the order for the age and credit, it seems as if I cannot use bubble sort to switch the first and last name because they are character array. I have to do this using struct and I have to print three tables. I was wondering if there was any other way I could do the whole thing.
As part of a larger project, I am trying to write a function that will allocate enough memory for a struct variable and assign values to its member variables after scanning them from the keyboard. In other words, I am trying to create a sort of a constructor function. The reason for this is because I think that's the best way to create a database-like program in c, where all the student_t variables will be stored in a student_t* array called classroom.
#include <stdio.h>
#include <stdlib.h>
#define N 10
#define STRLIM 50
typedef struct student{
char* name;
int age;
}student_t;
student_t* init_student(student_t* s);
int i=0;//its the array counter
student_t* classroom[N];
int main(int argc, char const *argv[]){
while(i<N){
// classroom[i]=(student*)malloc(sizeof(student));
init_student(classroom[i]);
classroom[i]->age=i;
printf("The age of student #%d is : %d \n",i,classroom[i]->age);
printf("the name of student #%d is : %s",i,classroom[i]->name);
i++;
}
printf("the size of the classroom is : %ld",sizeof(classroom));
return 0;
}//end of main()
student_t* init_student(student_t* s){
s=(student_t*)malloc(sizeof(student_t));
s->name=(char*)malloc(sizeof(char)*STRLIM);
fflush(stdin);
fgets(s->name,STRLIM,stdin);
return s;
}
Gdb ouput shown in the attached image here.
Please check out my repo.
I am guessing something about my build and datatypes is off .Thanks in advance.
Fields of Student: name, lastName, studentId, mid1Grade, mid2Grade, finalGrade, average
Fields of Course: courseName, courseCode, myStudentArray (array of Student structures),currentStudentCount
Functions:
void createNewStudent(struct Course *myCourse);
void setGradeOfStudent(struct Course *myCourse);
void findAndDisplayAverage(struct Course *myCourse);
struct Student * findStudentByID(int id, struct Course *myCourse);
void displayAverageOfAllStudents(struct Course *myCourse);
void displayAverageOfStudentsInInterval(struct Course *myCourse
ok so I have written the first function but there is an error which I dont understand. First of all the first function and what it does:
createNewStudent: Prompt the user to enter name, last name and id of the new student.Values entered by the user are assigned to the fields of the student residing in themyStudentArray of course variable pointed by myCourse. currentStudentCount will be updated so that it designates the slot allocated for the student inserted next.
and my implementation:
#include <string.h>
#include <stdio.h>
struct Student {
char name[50];
char lastname[50];
int id;
int mid1;
int mid2;
int final;
double average;
};
struct Course {
char courseName[50];
char courseCode[50];
struct Student myStudentArray[5];
int currentstudentcount;
};
void createNewStudent(struct Course * myCourse);
void setGradeOfStudent(struct Course * myCourse);
void findAndDisplayAverage(struct Course * myCourse);
struct Student * findStudentByID(int id, struct Course * myCourse);
void displayAverageOfAllStudents(struct Course * myCourse);
void displayAverageOfStudentsInInterval(struct Course * myCourse);
int main() {
struct Student * stud;
int input = 0;
scanf("%d", & input);
if (input == 1) {
createNewStudent(struct Course * myCourse);
}
}
return 0;
}
void createNewStudent(struct Course * myCourse) {
struct Student s1;
printf("Enter name: ");
scanf("%[^\n]%*c", s1.name);
printf("Enter Surname: ");
scanf("%[^\n]%*c", s1.lastname);
printf("Enter id: ");
scanf("%d", & s1.id);
}
When you call the function with the if(input == 1) it gives
error: expected expression before ‘struct’
but I dont understand this beacuse *myCourse is just a pointer to the Course struct isn't it ????
If I can understand this ı will be able to the the next functions I think
Is the function correct ?? I dont know why this doesnt work
Ok I tried to use the struct Student myStudentArray[5]; to get name, lastname,id like so (structs are the same)
void createNewStudent(struct Course *myCourse);
void setGradeOfStudent(struct Course *myCourse);
int main(){
struct Course *myCourse;
int input=0;
scanf("%d",&input);
if(input == 1){
createNewStudent(myCourse);
}
return 0;
}
void createNewStudent(struct Course *myCourse){
myCourse->currentstudentcount=0;
printf("Enter name: ");
scanf("%[^\n]%*c"
,myCourse->myStudentArray[myCourse->currentstudentcount].name);
printf("Enter Surname: ");
scanf ("%[^\n]%*c",
myCourse->myStudentArray[myCourse->currentstudentcount].name);
myCourse->currentstudentcount++;
}
I Keep getting
may be used uninitialized in this may be used uninitialized in this function [-Wmaybe-uninitialized]
and
Segmentation errors
void createNewStudent(struct Course * myCourse)
If you want to create new student, you should use the student struct as the parameter of this function instead of using struct Course.
void createNewStudent(struct Student *s1)
Then, this function becomes as:
void createNewStudent(struct Student *s1) {
printf("Enter name: ");
scanf("%49s", s1->name);
printf("Enter Surname: ");
scanf("%49s", s1->lastname);
printf("Enter id: ");
scanf("%d", & s1->id);
}
If you want to test, in main function, you can declare the value stud or the pointer to struct Student.
For example:
int main() {
struct Student stud;
int input = 0;
scanf("%d", & input);
if (input == 1) {
createNewStudent(&stud);
printf("name: %s\n Surname: %s\n id = %d\n", stud.name, stud.lastname, stud.id);
}
return 0;
}
The complete program for test:
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
struct Student {
char name[50];
char lastname[50];
int id;
int mid1;
int mid2;
int final;
double average;
};
struct Course {
char courseName[50];
char courseCode[50];
struct Student myStudentArray[5];
int currentstudentcount;
};
void createNewStudent(struct Student *s1);
int main() {
struct Student stud;
int input = 0;
scanf("%d", & input);
if (input == 1) {
createNewStudent(&stud);
printf("name: %s\nSurname: %s\nid = %d\n", stud.name, stud.lastname, stud.id);
}
return 0;
}
void createNewStudent(struct Student *s1) {
printf("Enter name: ");
scanf("%49s", s1->name);
printf("Enter Surname: ");
scanf("%49s", s1->lastname);
printf("Enter id: ");
scanf("%d", & s1->id);
}
The output:
#./test
1
Enter name: abc
Enter Surname: def
Enter id: 100
name: abc
Surname: def
id = 100
Update for your question in the comment:
If you want to store student info in an array, you can change the code to:
struct Student myStudentArray[5];
int input = 0;
scanf("%d", & input);
if (input == 1) {
for (int i = 0; i < 5; i++) {
createNewStudent(&myStudentArray[i]);
}
for (int i = 0; i < 5; i++) {
printf("name: %s\nSurname: %s\nid = %d\n", myStudentArray[i].name, myStudentArray[i].lastname, myStudentArray[i].id);
}
}
For Course structure you can create one function as the function createNewStudent but for struct Course to create the new course. After creating new 5 students (for example the code above), you can copy the myStudentArray to new_course.myStudentArray. Then now you have the info of 5 students in new_course. When you copy value from an array to another, you can use memcpy or using one loop to copy each element from one array to another one. Do not use something like myStudentArray = new_course.myStudentArray for the array.
You are making a declaration as a parameter of the createNewStudent() function. In C, functions require expressions as parameters, which is why you got the error message "expected expression...".
So, just create the struct pointer before you call the function:
if (input == 1) {
struct Course *myCourse = malloc(sizeof(struct Course));
createNewStudent(myCourse);
}
Notice the use of malloc(), which returns a pointer to a place in memory of sufficient size to hold that particular Course struct. When dealing with pointers to structs, you need to allocate memory for the structs that will ultimately be pointed to, in order to avoid dereferencing unallocated regions of memory.
In your function CerateNewStudent, the proper way to address the variables into which to place the data read by scanf should be:
myCourse->myStudentArray[myCourse->currentstudentcount].name
as the variable to read name into. Use this syntax for all data items to read. After that, increment the counter:
myCourse->currentstudentcount++;
Note: what is missing in all your functions (and in the assignment?) is a way to create a course. The students created are all added to courses. First a course should be created and then students can be added to it.
Hey guys im learning c and im currently working on stack, structure and pointer. Im using visual studio to do my the program and whenever i enter my input the program will crash. I'm able to scope down that the error is coming from the product name. I am also quite confused since it includes pointer character. Anyone can point out my mistakes? thank you
HERE ARE MY CODES
#include<stdio.h>
#include<string.h>
#define MAX 10
int top = -1;
struct Product {
int prodId;
char *prodName;
};
struct Product arrP[MAX];
struct Product pop();
void push(int id, char *name);
int isFull();
int isEmpty();
struct Product pop()
{
struct Product temp;
temp = arrP[top];
top--;
return temp;
}
void push(int id, char *name)
{
top++;
arrP[top].prodId = id;
strcpy(arrP[top].prodName,name);
}
int isFull()
{
if (top == MAX)
return 1;
else
return 0;
}
int isEmpty()
{
if (top == -1)
return 1;
else
return 0;
}
int main()
{
int myID;
char *myName;
//Push the value
printf("Enter the Product id: ");
scanf("%d", &myID);
printf("Enter the Product Name: ");
scanf("%s", &myName);
push(myID, &myName);
printf("%d %s", arrP[top].prodId ,arrP[top].prodName);
}
There are few simple bugs which you can avoid my listening to compiler warning while compiling with -Wall flag.
Case 1:- variable myId suppose to be a integer variable, not a pointer variable. If you want it to be pointer variable then you should allocate memory for it first.
int *myID;
printf("Enter the Product id: ");
scanf("%d", &myID);
Replace with
int myID;
printf("Enter the Product id: ");
scanf("%d", &myID);
Case 2:- variable myName supposed to be array of characters as you want to store product name into it.
char myName;
printf("Enter the Product Name: ");
scanf("%s", &myName);
Replace with
char myName[50];
printf("Enter the Product Name: ");
scanf("%s", myName);
While calling push() function just pass the myName. For e.g
push(myID, myName);
Also this statement
strcpy(arrP[top].prodName,name);
causes problem as prodName is pointer member in of structure, you should allocate memory dynamically for this and then do copy.
arrP[top].prodName = malloc(SIZE);
strcpy(arrP[top].prodName,name);
When you are getting the input using %s in character type variable, the memory adjacent to the address of the char variable gets overwritten thus can cause program crash. if you want to enter a string, you can try it by defining an array of characters (as char my name[MAX], MAX can be a size suitable to you).
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct data{
char name[20];
char lastname[25];
int age;
}person;
void insert(person *p,int *num);
int main()
{
int num;
person p;
insert(&p,&num);
printf("Name: %s",p[0].nome); /* Here i would print the first struct by
my array, but: is not array or not pointer Why?? */
}
void insert(person *p, int *num)
{
int dim;
person *arr;
printf("Insert how many people do you want? "); /* How many index the
array should have */
scanf("%d",&dim);
arr = (person *) malloc(dim*sizeof(person)); /* I'm not sure for
this explicit cast. */
for(int i = 0; i < dim; i++)
{
printf("Insert name: ");
scanf("%s",arr[i].name);
printf("Insert lastname: ");
scanf("%s",arr[i].lastname);
printf("Insert age:': ");
scanf("%d",&arr[i].age);
}
*num = dim;
*p = *arr;
}
I've tried: `person *insert(int *num)
And it's works,but how can pass an array reference?`
This programm should ask how many person do you want to insert ( in function insert) and with a for, he should ask name,surname,age.
After the insert, he should print, but for quick, i would tried with first element (index) of array (structs).
You can't return entire array from the function, but you can return the base location of the array. For example you can do like this : person *insert(int *sz);. But i see in your code you're passing &p and the &num variable into the insert method, maybe you want to modify them within that function and manipulate it afterwards in your main(). For that i would have these recommendations:
Change Line 16 person p to person *p. Since p is supposed to hold base value of an array. Remember array name is nothing but a base address to the first element of the list.
Change your function definition to recieve person** rather than person*. Since you want to modify a pointer variable and therefore you'd need a pointer to a pointer variable. Change it like this:` void insert(person **p, int *num)
Free the memory after usage; add a free(p) at the end of main.
`