CODEWITHSUNDEEP
carrayspointers
Alexander
Alexander

Reputation: 29

C -- Trouble with pointers

I am new to C, know some Java. Trying to write a program that accepts 2D array that represents a directed adjacency matrix, and two numbers, scans the array and returns true if there is a directed path between them (top-down).

I am running into a problem with C implementation. Apparently I have to use pointers to values in array, whilst in Java I could've use values from array (compare, return to function, etc).

I'm pretty sure the logic is in place, I just need help with allocating '*'s in the right places and amounts.

Here's the code:

#include <stdio.h>

#define N 12

typedef int bool;
enum {false, true};

typedef struct adj_mat{
    int A [N][N];
}adj_mat;



int path(struct adj_mat A, int origin, int dest){
    int i;
    if (origin == dest) return true;
    for (i = 0; i < sizeof(A);i++){
        if (A[origin][i]){
            return path (A, i, dest);
        }
    }
    return false;
}

Thanks in advance.

Upvotes: 1

Views: 72

Answers (2)

typ1232
typ1232

Reputation: 5587

sizeof(A)

This probably does not give you what you expect. It is the number of bytes, not the number of elements.

A[origin][i]

Here you are trying to index the struct adjmat which doesn't work. You probably wanted to index the member A. Try:

A.A[origin][i]

It would probably be a good idea to rename adj_mat A to something else to avoid confusion.

You should also pass the address of A to the function and use adj_mat* as the argument type. If I understand correctly you want the recursion to operate on the same object.

Upvotes: 0

timrau
timrau

Reputation: 23058

for (i = 0; i < sizeof(A);i++){

This should be for (i = 0; i < N; i++){.

Also, your algorithm may not terminate since it didn't take care of cycles in graph.

Upvotes: 2

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