Binary search for specific value in array of structs

Question

I wrote this function that uses a binary search to look for a specific value in an array of structs. Why doesn't it compile?

I'm getting this error:

prog.c:224: error: subscripted value is neither array nor pointer
prog.c:226: error: subscripted value is neither array nor pointer

This is the function:

int FieldSearch(Field *pArr, int size, int val)
{
    int low=0,high=size-1, middle;
    while (low <= high)
    {
        middle = (low + high)/2;
        if (val == pArr->Id[middle])
            return middle;
        else if (val < pArr->Id[middle])
            high = middle -1;
        else
            low = middle +1;
    }
    return NOT_FOUND;
}

This is the field struct:

typedef struct field
{
        char Id;
        Coordinates location;
        int area;
        int price;
} Field;

Maybe the prototype is wrong...

id is integer i mean %d, yes this is c...

talmordaniel
– talmordaniel

2011-06-04 09:11:03 +00:00
Commented Jun 4, 2011 at 9:11 — talmordaniel
– talmordaniel, Commented Jun 4, 2011 at 9:11

Tony The Lion · Accepted Answer · 2011-06-04 09:11:37Z

2

Your problem is this statement:

pArr->Id[middle]

It looks like, but I don't have nearly enough info, that your member Id is not a pointer or an array, but merely a variable. So you cannot access it with an operator[]. You should show us what this Field object looks like.

I'm guessing you should do something like this

(pArr + middle)->Id so this will access the element of the Field array you passed into your function. Then you do have to pass in an actual array of Field structures, for this to work.

answered Jun 4, 2011 at 9:11

Tony The Lion

63.6k71 gold badges252 silver badges427 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

talmordaniel Over a year ago

this is the field struct: typedef struct field { char Id; Coordinates location; int area; int price; } Field;

Tony The Lion Over a year ago

Id is not an array, you cannot access it with the operator[], as I said

TheFogger · Accepted Answer · 2011-06-04 09:15:30Z

1

If you want to search the "array" pArr, you need to put the brackets directly behind the identitifier. This should work:

pArr[middle].Id

answered Jun 4, 2011 at 9:15

TheFogger

2,4391 gold badge21 silver badges22 bronze badges

1 Comment

talmordaniel Over a year ago

ok that seem to work.. i guess that problem was that i didn't put the brackets at right place..this is the fix line if (val == pArr[middle].Id) return middle; else if (val < pArr[middle].Id) thnx guys!

Collectives™ on Stack Overflow

Binary search for specific value in array of structs

2 Answers 2

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related