I'm not sure how to make this function non-recursive. Any ideas?:

void foo(int a, int b){
    while( a < len && arr[a][b] != -1){            
        if(++a == len){
            a = 0;
            b++;
        }
    }
    if( a == len){
        size++;
        return;
    }
    if( a < (len-1)){
        arr[a][b] = 1;
        arr[a][(b+1)] = 1;
        foo(a, b);
        arr[a][b] = -1;
        arr[a][(b+1)] = -1;
    }
    if( a < (len-1) && arr[(a+1)][b] == -1){
        arr[a][b] = 0;
        arr[(a+1)][b] = 0;
        foo(a,b);
        arr[a][b] = -1;
        arr[(a+1)][b] = -1;
    }

}