Having problems of skipping loops after scanf

Question

I am in my first year of uni, studying c. I am doing one of my assignment but having problems with one of the loop just skipping. I am using Codeblocks with the GNU GCC compiler. Please ignore option 2, 3, 4.

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

int main()
{
    int num, i, numscr;
    float grade[2021];
    int id[2021];
    int opt;
    float avg[2021];
    float sum=0.0;
    do {
        printf("\nOption 1: Enter student's info\n");
        printf("Option 2: Print out student's info\n");
        printf("Option 3: Find the student with the lowest and highest grade\n");
        printf("Option 4: Exit\n");
        printf("Enter option: ");
        scanf("%d", &opt);
        if(opt==1)
        {
            printf("\n\tEnter the amount of student (Amount>=2): ");
            scanf("%d", &num);
            printf("\tEnter the amount of subject: ");
            scanf("%d",&numscr);
            for(i=0; i<num; i++)
            {
                printf("\n\tEnter student's id: ");
                scanf("%d", &id[i]);
                for(i=1; i<=numscr; i++)
                {
                    printf("\tEnter point of subject %d: " ,i);
                    scanf("%f", &grade[i]); /*The loop skips here.
                    After entering the grade for each subject,
                    it just skips whatever student's id and subject's point there are left.
                    I think the problem is with the sum+=grade[I]; but I don't know why*/
                    sum+= grade[i];
                }
            }
            avg[i]=sum/numscr;
        }
    } while(opt>0 && opt<=3)
    return 0;
}

Sorry if the code doesn't look great, I forgot to format it until now. If anyone can help then I really appreciate it, I've been racking my head for the entirety of the afternoon now.

Answer 1

You used i for both loops of for(i=0; i<num; i++) and for(i=1; i<=numscr; i++) . This means that the inner loop will use i and affect the outer loop.

Use another variable (for example, j ) for the inner loop to fix.

Also it looks like you forgot to initialize sum before calculating the average for each query.