How to complete this for-loop that calls a function [closed]

Question

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.

Closed 9 years ago.

I am having trouble trying to make a certain for-loop continue to completion in the 1D Queens problem.

First, I used goto statements for everything. Now I am trying to get rid of the goto statements by using functions instead. I will eventually get rid of all of them, but I am focusing on NR (new row) and backtrack first, since they are meant to call each other.

The for loop I am having trouble with is the one that checks if a position is safe for a queen. I point out the for-loop that does not complete in the comments.

//forward declarations
int backtrack (int board[], int& c_position);

//NR: q[c]++;
//if (q[c]==8) goto backtrack;

void NR (int board[], int& c_position) //new row
{
    board[c_position]++;
    if (board[c_position]==8) {backtrack(board, c_position);}
}

int backtrack (int board[], int& c_position)  // backtrack
{
    c_position--;
    if (c_position==-1) {system("PAUSE"); exit(1);}
    NR(board, c_position);
}


int main ()
{

int q[8] = {0};  //1D array, the board, all set to 0;
int c=0;
int count=0;


NC: c++; //new column
    if (c==8) goto print;
    q[c]=-1;

NR(q, c);


    //test to see if position is safe
    for (int i=0; i<c; i++) //this is the for loop I am having trouble with
    {
    if ( (q[i]==q[c]) || ((c-i)==abs(q[c]-q[i])) ) { NR(q, c); }
    }

    goto NC;

print: //printing the 1D board gives us a single line, where each number represents a row where a queen is
        count++;
        cout << count << endl;
      for(int j = 0; j <= 7; j++)
      {
         cout << q[j] << " ";
      }
       cout << endl;
        backtrack(q, c);

        system("PAUSE"); return 0;

}

Answer 1

You're passing c by reference to a function that passes it to another function that decrements it.

That appears to foil your (outer goto-based) loop's attempt to increment it.

Anyway, that's what I'd look at more closely.