C 编程：我的代码有问题

Question

i can't find the error in my code can you guys help me? here is the code:

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

struct job
{
char jobname[50];
char jobtype;
float executingtime;
int jobpriority;
};

int main(void)
{
int n;
int i=0,j=0;
int max=0;
struct job jobdetails[n];

Then i ask the user to keyin the details of job (only jobs of Type A or Type B with Type B has higher priority than Type A)

printf("Please enter number of jobs: ");
scanf("%d",&n);

for (i=0;i<n;i++)
{
    printf("\nPlease enter the job name: ");
    scanf("%s",&jobdetails[i].jobname);
    printf("Please enter type of job (A or B): ");
    scanf("%s",&jobdetails[i].jobtype);
    if (jobdetails[i].jobtype == 'A' || jobdetails[i].jobtype == 'a')
    {
        jobdetails[i].jobpriority=1;
    }
    else if (jobdetails[i].jobtype == 'B' || jobdetails[i].jobtype == 'b')
    {
        jobdetails[i].jobpriority=2;
    }
    else
    {
        printf("Invalid Job Type\nPlease Try Again");
        return -999;
    }
    printf("Please enter the executing time of job (in s): ");
    scanf("%f",&jobdetails[i].executingtime);
}

Here is the part which I wanna print the jobs from highest priority to lowest:

do
{
    for (j=1;j<n;j++)
    {
        if (jobdetails[max].jobpriority < jobdetails[j].jobpriority)
        {
            max=j;
        }
    }

    printf("\nJob Name: %s ",jobdetails[max].jobname);
    printf("\nJob type: %c ",jobdetails[max].jobtype);
    printf("\nJob Executing Time: %.f in s \n",jobdetails[max].executingtime);
    max=n-1;
    n=n-1;

}while (n!=0);

return 0;

}

sometimes i got the correct output but sometimes not. here is the output i got:

correct: enter image description here incorrect: enter image description here

I appreciate for your help, Thank you!

Answer 1

At least these problems:

Using "%s" without a width limit

"%s" directs input to form a string . For input like "Hello", that needs 5 + 1 (for the appended '\0' ) bytes.

char jobname[50];
...
// scanf("%s",&jobdetails[i].jobname);
scanf("%49s", jobdetails[i].jobname);
//            ^ ----- Do not use & when the object is an array.

0 width is no good

The below code lacks a width, yet the width should be 0 as the location to save the string has only enough room to save the null character .

char jobtype;
...
// scanf("%s",&jobdetails[i].jobtype);  // Bad
// scanf("%0s",&jobdetails[i].jobtype); // Bad too.

Here OP likely wants to read and save 1 non-white-space character.

//     v- Note the space to consume optional leading white-space.
scanf(" %c",&jobdetails[i].jobtype);

or if still wanting jobtype as a string .

char jobtype[2];
...
scanf("%1s", jobdetails[i].jobtype);

Better code checks the return value of scanf()

Did the input succeed? Find out.

if (scanf(....) != Expected_Counvertion_Count) {
  Handle_Error();
}   

Better code does not use scanf()

Use fgets() to read a line of user input in a string and then parse those strings for job name, type, time, priority.