Stuck in a maze loop - c++

Question

The problem
I'm new to this sort of programming, and my C++ maze solver is stuck in a loop.
The maze is a simple char 2-D matrix with an asterisk (*) for a valid path square, and a slash (/) for a wall square.
Why doesn't the program stop when it finds a '/'?
# include < iostream >
using namespace std;
char lab[6][6] =
{ { '/','/','/','/','/' },
{ '/','*','/','/','/' },
{ '/','*','*','*','/' },
{ '/','/','*','/','/' },
{ '/','/','*','/','/' },
{ '/','/','*','*','*' } };
int x, y;
void run(char lab[][6], int, int);
bool movU() // Move Up
{
if (lab[x][y - 1] == '*')
return true;
else
return false;
}
bool movR() // Move right
{
if (lab[x + 1][y] == '*')
return true;
else
return false;
}
bool movD() // Move Down
{
if (lab[x][y + 1] == '*')
return true;
else
return false;
}
bool movL() // Move Left
{
if (lab[x - 1][y] == '*')
return true;
else
return false;
}
void run(char lab[][6], int x, int y)
{
if (movU() == true) // I'm getting stuck right here
run(lab, x, y - 1); // Getting negative numbers here
else if (movR() == true)
run(lab, x + 1, y);
else if (movD() == true)
run(lab, x, y + 1);
else if (movL() == true)
run(lab, x - 1, y);
else
cout << "Error" << endl;
}
int main()
{
x = 1, y = 2; // Start position
run(lab, x, y);
return 0;
}

Answer 1

Besides the global scoping problem with x and y, you haven't done anything to keep the subscripts from running over the edge of the maze into random memory locations. As a result, y continues to decrement, and you back up through memory looking for an asterisk. Since you also recur, you continue this until you blow all your stack space.
Also, you don't seem to be comfortable with boolean values yet: you do a lot of extra work to deal with constants true and false, rather than simply using the value of a boolean expression.
I've fixed these items in your code:
# include <iostream>
using namespace std;
char lab[6][6] =
{
{ '/','/','/','/','/' },
{ '/','*','/','/','/' },
{ '/','*','*','*','/' },
{ '/','/','*','/','/' },
{ '/','/','*','/','/' },
{ '/','/','*','*','*' }
};
void run(char lab[][6], int, int);
bool movU(int x, int y) // Move Up
{
return x >= 0 && y >= 1 &&
x < 6 && y < 6 &&
lab[x][y - 1] == '*';
}
bool movR(int x, int y) // Move right
{
return x >= 0 && y >= 0 &&
x < 5 && y < 6 &&
lab[x+1][y] == '*';
}
bool movD(int x, int y) // Move Down
{
return x >= 0 && y >= 0 &&
x < 6 && y < 5 &&
lab[x][y + 1] == '*';
}
bool movL(int x, int y) // Move Left
{
return x >= 1 && y >= 0 &&
x < 6 && y < 6 &&
lab[x-1][y] == '*';
}
void run(char lab[][6], int x, int y)
{
cout << "ENTER run; x = " << x << "\ty = " << y << endl;
if (movU(x, y)) // I'm getting stuck right here
run(lab, x, y - 1); // Getting negative numbers here
else if (movR(x, y))
run(lab, x + 1, y);
else if (movD(x, y))
run(lab, x, y + 1);
else if (movL(x, y))
run(lab, x - 1, y);
else
cout << "Error" << endl;
}
int main()
{
// x = 1, y = 2; // Start position
run(lab, 1, 2);
return 0;
}
This stays within bounds ... and loops until it runs out of stack space. You need to add code to avoid rechecking ground you've already visited. For instance, you can mark the location with another character, such as an underscore.
You also need to recognize when you're done. What marks the maze exit? You'll need a check in your run routine for that.