While loop

[MrBeavis]

Good Morning Coders,
I need a quick help with my while loop, I have a dynamically allocated array that increases with each input of an integer value, I wish to exit the loop once the user enters -1 and not have that value in the array. I've tried a combination of ideas but I'm stumped. Here is what i have so far

int main(int argc, char const *argv[])
{
	int index = 1;
	int* iptr = new int[index];
	int count = 0;



	do //input will continue till -1 is entered
	{
		cout << "Enter Integer Value: ";
		cin >> iptr[index];
		cout << "1" << endl;
		if(iptr[index] != -1)
		{
			cout << "2" << endl;
			count++;
			if(count >= index)
			{
				cout << "3" << endl;
				index++; //increase by 1
				int* temp = new int[index];//create a new bigger array
				for(int i = 0; i < index; i++)//copy old array to new array
				{
					temp[i] = iptr[i];
					cout << "4" << endl;
				}
				delete [] iptr;//free up old array memory
				iptr = temp;//points to new array
				cout << "5" << endl;
			}
		}	
		cout << "6" << endl;
	}while(iptr[index] != -1);

[LB]

int x;
while((std::cin >> x) && x != -1)
{
    //deal with x
}

[MrBeavis]

tried that the other day, for some reason it hangs before entering the loop

[LB]

If that were true, your code would never reach line 13 where it outputs "1".

[MrBeavis]

i got it, sorry you were right my cout was in the wrong place :).

although now i am thoroughly confused. I believe i have a memory leak somewhere as it runs sometimes and other times crashes. here is the full code

#include <iostream>
using namespace std;

void SelectSort(int [], int);
float MeanCalc(int [], int);
float MedianCalc(int* [], int);

int main(int argc, char const *argv[])
{
	int index = 0;
	int input;
	int* iptr = new int[index];
	int count = 0;


	cout << "Enter Integer Value: ";
	while((cin >> input) && input != -1) //input will continue till -1 is entered
	{
		if(input != -1)
		{
			iptr[index] = input;
			cout << "1" << endl;
			cout << "2" << endl;
			count++;
			if(count >= index)
			{
				cout << "3" << endl;
				index++; //increase by 1
				int* temp = new int[index];//create a new bigger array
				for(int i = 0; i < index; i++)//copy old array to new array
				{
					temp[i] = iptr[i];
					cout << "4" << endl;
				}
				delete [] iptr;//free up old array memory
				iptr = temp;//points to new array
				cout << "5" << endl;
			}
		}	
		cout << "6" << endl;
		cout << "Enter next integer: ";
	}

	SelectSort(iptr, index); //sorts the input into ascending order for MedianCalc

	for(int i = 0; i < index; i++)//error checking the sort algorithm works
	{
		cout << "X" << iptr[i] << endl;
	}

	cout << "The Mean of the Numbers Entered is : " << MeanCalc(iptr, index) << endl; //calls the MeanCalc and outputs mean

	//MedianCalc(ptrarr, index);



	return 0;
}

void SelectSort(int sort[], int size) // select sorting algorithm
{
	int min_i;
	int min_e;

	for(int i = 0; i < (size - 1); i++)
	{
		min_i = i;
		min_e = sort[i];
		for(int j = i + 1; j < size; j++)
		{
			if(sort[j] < min_e)
			{
				min_e = sort[j];
				min_i = j;
			}
		}

		sort[min_i] = sort[i];
		sort[i] = min_e;
	}

}

float MeanCalc(int input[], int index)// calculates the mean
{
	int SumTotal;
	int* ptr;
	float Mean;

	ptr = input; //allocates pointer to first element in array

	for(int i = 0; i < index; i++)
	{
		SumTotal += (*(ptr + i));//adds the elements together.. is this pointer arithimetic though?
	}

	Mean = SumTotal / index;

	return Mean;
}

/*float MedianCalc(int* ptrarr[], int index)
{
	float Median;
	float middle;

	if(index % 2 == 0)
	{
		middle = (index / 2) - 1;
		cout << *ptrarr[middle] + *ptrarr[middle + 1] << endl;
		cout << *ptrarr[middle + 1] << endl;
		Median = (*ptrarr[middle] + *ptrarr[middle + 1]) / 2;
		cout << Median << endl;
	}
}*/

any help would be great

[LB]

On line 12 you dynamically create an array of size 0. Line 21 is then guaranteed undefined behavior.

[MrBeavis]

sorry but what do you mean?
weve only just started learning this

[giblit]

Line 10 index has a value of 0 then on line 12 when you create your dynamic array of size index you are creating an empty array.

[MrBeavis]

oh ok I see what you mean, if i change the value to 1 will that solve the issue?

when i cout my sort as well im getting some random values. what is the cause of that?

this is with the input 15 -9

Enter next integer: -1
X9
X11
X12
X13
X14
X15
X10098048
X117242368
The Mean of the Numbers Entered is : 1.59176e+00

[cire]

oh ok I see what you mean, if i change the value to 1 will that solve the issue?

No. You will continue to access outside the bounds of the array. See lines 29 and 21.

[MrBeavis]

ok im going to have go back over pointers