segmentation fault with pointer array - c++

Question

I am a getting a segment fault when trying to input data for my array of pointers. Im pretty new to coding so any help would be great. My task was to make an array of pointers then display, swap them around and than sort them
#include <iostream>
using namespace std;
float getValueFromPointer(float* thePointer)
{
return *thePointer;
}
float* getMinValue(float* a, float* b)
{
if (*a < *b)
{
return a;
}
else
{
return b;
}
}
int main()
{
int arraySize;
cout << "Enter the array size: ";
cin >> arraySize;
float** speed = new float*[arraySize]; // dynamically allocated array
for(int i = 0; i < arraySize; i++)
{
cout << "Enter a float value: ";
cin >> *speed[i];
}
// Core Requirement 2
for (int i = 0; i < arraySize; i++)
{
float value = getValueFromPointer(*speed+i);
cout << "The value of the element " << i << " is: ";
cout << value << endl;
}
//float *pointerToMin = getMinValue(&speed[0], &speed[arraySize - 1]);
//cout << *pointerToMin << endl;
delete [] speed;
speed = NULL;
return 0;
}

Answer 1

You’ve only allocated space for the outer array but you need to also allocate space for each of the internal floats.
So before calling this line:
cin >> *speed[i];
You need to first allocate space for it:
speed[i] = new float;

Answer 2

Your problem is that you've allocated an array of float pointers. You need to allocate an array of floats. So currently you have no memory allocated for the actual floats. If you do this, you'll allocate that memory:
float *speed = new float[arraySize];
You don't have any need for a 2D/jagged array that I can see. If you start with the code above, the compiler errors should lead you right in the direction. (Basically you will start removing * from a lot of places in your code.)
EDIT
Based on your requirement that I misunderstood, a possible approach is the following. The other answer (the one that isn't mine) makes sense in broader scenarios than this, but hopefully this is sort of another angle to think about that rather arbitrary problem you're trying to solve:
int main()
{
float *pFloats = new float[10];
float **ppFloats = new float*[10];
//assign float values and pointers to them in same loop
for (int i = 0; i < 10; i++)
{
pFloats[i] = i;
ppFloats[i] = &pFloats[i];
}
//swap two arbitrary pointers
float *pTemp = ppFloats[4];
ppFloats[4] = ppFloats[5];
ppFloats[5] = pTemp;
//print our float array
for (int i = 0; i < 10; i++)
printf("%f\n", pFloats[i]);
//print our float array *through* our pointers
for (int i = 0; i < 10; i++)
printf("%f\n", *ppFloats[i]);
delete[] ppFloats;
delete[] pFloats;
}
Ignore the hard-coded constants, etc...The point here is that I've created a contiguous memory area for the floats, and then created an array of float pointers on top of it. Note that I can sort my pointer array with zero impact on the original array. There are much smarter ways to do this, but...looks like you're learning about raw pointers, so...
Contrast with the other answer which creates jagged memory for the floats (1 at a time, on demand, not necessarily contiguous).