A silly mistake is crashing my code. Please help me.

[Ltp]

I want to display, whether its reachable from a node to another or not.
Here is my code:

#include <iostream>
#include <ctime>
using namespace std;

class Queue{
    private:
        int *queue;
	int q;
        int front;
	int rear;
	bool empty;
    public:
	Queue();
        Queue(int);
	int que_size();
	int curr_size();
        void enqueue(int);
        void dequeue(int&);
        bool is_empty();
	bool is_full();
	bool not_exist(int[], int, int &);
};

Queue::Queue()
{
    q = 30;
    queue=new int[q];
    front=0;
    rear=0;
    empty = true;
}

Queue::Queue(int x)
{
    q=x;
    queue=new int[q];
    front=0;
    rear=0;
    empty = true;
}

void Queue::enqueue(int x)
{
	if(!is_full()){
	queue[rear] = x;
	rear = (rear+1)%q;

	if(empty)
	empty = false;
	}
}

void Queue::dequeue(int &x)
{
	if(!is_empty()){
		x = queue[front];
		front = (front+1)%q;

		if(front == rear)
			empty = false;
	}
}

bool Queue::is_empty()
{
	return empty;
}

bool Queue::is_full()
{
	if(!empty && front == rear)
		return true;
	return false;
}

bool Queue::not_exist(int b[], int n, int &y)
{
	int i;
	for(i=0; i<n; i++){
		if(b[i] != y)
			return true;
		return false;
	}
}


int main()
{
	int a[50][50];
	int b[50];
	int n, s, d;
	int i, j, k=0;
	int x;
	int distance, p, row, col;
	
	cout<<"How many nodes do you have?\n";
	cin>>n;

	cout<<"Enter percentage: ";
	cin>>p;

	Queue q1(n);


	for(i=0; i<n; ++i){	
		a[i][i] = 1;
		for(j=i+1; j<n; ++j){
			a[i][j] = rand()%2;
			a[j][i] = a[i][j];
		}
		cout<<endl;
	}

	distance = n - (n*((float)p/100));
	
	for(i=0; i<distance; ++i){
        row=rand()%n;
        col=rand()%n;
        if(row==col)
            a[row][col]=1;
            else{
		a[row][col]=0;
		a[col][row]=0;
	    }
    }

	cout<<"Your matrix is:\n"<<endl;
	for(i=0; i<n; ++i){
		for(j=0; j<n; j++)
			cout<<a[i][j]<<"  ";
		cout<<endl<<endl;
	}

	cout<<"Enter your source & destination: ";
	cin>>s>>d;

	q1.enqueue(s);

	while(!q1.is_empty()){ 

		q1.dequeue(x);
		b[k] = x;

		if(x == d)
		cout<<s<<" -> "<<d<<" is reachable.\n";
		else{
		for(j=0; j<n; ++j){
			if(a[x][j] == 1){
				if(q1.not_exist(b, 50, j) == true){
				k++;
				q1.enqueue(j);
			        }
		        }
		break;
		}
	        }
        }

	cout<<endl;

	system ("Pause");
	return 0;
}

Why my code crashes? Plz help me.

[Ltp]

else{
		for(j=0; j<n; ++j){
			if(a[x][j] == 1){
				if(q1.not_exist(b, 50, j) == true){
				k++;
				q1.enqueue(j);
			        }
		        }
		break;
		}
	        }

The problem in my code is in here. But I cant fix the specific error.

[LB]

Have you tried fixing your indentation first?

[cire]

Actually, I think the problem is on line 60.

Where it manifests is on line 148. (Uninitialized memory is accessed to return the value of x leading to an out of bounds array access on a.)

Also, Queue::not_exist should not be a method of Queue, nor is it correct.

Equivalent to current not_exist:

bool not_exist(int b[], int n, int &y)
{
    if ( n )
        return b[0] == y ;
}

[Ltp]

So, What should I change?
Do I have anything to add?

[cire]

So, What should I change?

The code. Do you have a more specific question?

[Ltp]

Ya.
My code is almost complete. Can you plz solve the problem?

[LB]

He already did solve your problem: he found what was causing the error and explained it to you.

[cire]

Can you plz solve the problem?

No. That task is yours.