exception in my program

[kyle11778]

exception: std::out_of_range at memory location

not sure what this means. below is the function that it yells at me. Exception happens after the System("pause");(i use pause to debug)

void run(int a,int b, bool& state){// (x,y,pervious direction)
	// display row col grid
	// check if surrounding spaces are the exit,if so return number of spaces traveled
	// check if any openings up,right,bottom,down
	// if direction is open then run in that direction with new position
	// if all directions closed then trapped at memory location 
	maze[a].at(b) = '@';

	cout << "      Row: " << a << "    Col: " << b << endl;
	cout << " 0123456789" << endl;
	for(int i = 0; i < 10; i++){
		cout << i << maze[i] << endl;
	}
	if(a != 0){
		if(maze[a--].at(b) == 'E'){state = true;return;}}
	if(b != 9){
		if(maze[a].at(b++) == 'E'){state = true;return;}}
	if(a != 9){
		if(maze[a++].at(b) == 'E'){state = true;return;}}
	if(b != 0){
		if(maze[a].at(b--) == 'E'){state = true;return;}}
	system("pause");
	if(a != 0){
		if(maze[a--].at(b) != '+' && maze[a--].at(b) != '@' && a != 0){run(a--,b,state);}}
	if(b != 9){
		if(maze[a].at(b++) != '+' && maze[a].at(b++) != '@' && b != 9 && state == false){run(a,b++,state);}}
	if(a != 9){
		if(maze[a++].at(b) != '+' && maze[a++].at(b) != '@' && a != 9 && state == false){run(a++,b,state);}}
	if(b != 0){
		if(maze[a].at(b--) != '+' && maze[a].at(b--) != '@' && b != 0 && state == false){run(a,b--,state);}}
	
	return;

}

thanks for any help everyone

[ne555]

Try to use a debugger instead.
http://www.cplusplus.com/reference/stl/vector/at/
So b<0 or b>=maze[_].size()

Edit: Sorry, I could never understand this behaviour:
maze[a--].at(b) != '+' && maze[a--].at(b) != '@' && a != 0 What is the value of a in every evaluation?

[kyle11778]

maze[] is an array of strings with a and b being a position within that 10x10 array. + represents a wall and '@' is where you have already gone. this is a maze program. get to the E and your safe but the program does it itself recursively

so as long as the next position (up,left,down,right) isn't a wall or you have not gone that direction or it is not out of bounds of the array then keep going in that direction

[ne555]

The exception is telling that b is out of bounds.
(I'm not sure of this) Suppose that a=6

if(a != 9){
		if(maze[a++].at(b) != '+' && //at the end of the line a=7
                maze[a++].at(b) != '@' && //at the end of the line a=8
                a != 9 && state == false){
                    run(a++,b,state); //at the end of the line a=9
                }
        }
	if(b != 0){
		if(maze[a].at(b--) != '+' && 
                maze[a].at(b--) != '@' && 
                b != 0 && state == false){
                     run(a,b--,state); //here you are analysing in a=9, you jump from 6 to 9 (that's cheat)
                }
       }

Just check the neighbours with a+1, instead of a++ (I think that the secondary effect is causing you trouble)

[kyle11778]

yeah i got that now, thanks i got it working now