Max, Min, Avg function for an array in C++ - c++

Question

I am being tasked with writing a function that takes as parameters an array of doubles, the size of the array, and then 3 pass-by-reference parameters called min, max, and avg. My function must: process the array data to find the minimum value (min), maximum value (max), and calculate the average (avg), each of which gets assigned to the corresponding reference parameter so that the calling function will be able to see those values. I am fairly new to coding and am very confused in what my error is the main function included below, any help would be greatly appreciated.
#include <iostream>
using namespace std;
void normalizeMinMaxAvg(double data[], int size,double& min, double&
max, double& avg)
{
max = 0;
min = 0;
//int amount = size;
int count = 0;
int sum = 0;
int i;
avg = 0;
for (i=0; i < size; i++)
{
count++;
sum += i;
if ( i > max)
{
i=max;
}
else if (i < min)
{
i=min;
}
}
avg = sum/count;
}
int main ()
{
double data[]={10.0,0.0,20.0,30.0};
cout << normalizeMinMaxAvg (data, 4, min, max, avg);
return 0;
}

Answer 1

Just provide variables that can be passed to that function, and output these like follows:
int main ()
{
double data[]={10.0,0.0,20.0,30.0};
double min, max, avg;
normalizeMinMaxAvg (data, 4, min, max, avg);
cout << "min = " << min << "\n";
cout << "max = " << max << "\n";
cout << "avg = " << avg << "\n";
return 0;
}
Also inside your function use the data from the array to calculate min and max:
if ( data[i] > max)
{
max = data[i];
}
else if (data[i] < min)
{
min = data[i];
}

Answer 2

Few problems:
deal with the empty data array case first.
set min and max to the first element of the array (not to zero). Think about what if the numbers are all negative. Will max contain the right answer?
You want to find the maximum and minimum elements so you have to use the data contained in data
if ( data[i] > max){
max=data[i];
}
Same goes for the min case.
normalizeMinMaxAvg does not return so you cannot use it in a cout expression. You can print the parameters directly.
Here is a working version of your code.
void normalizeMinMaxAvg(double data[], int size,double& min, double&
max, double& avg)
{
if(size<=0)
return;
min= max = data[0];
int count = 0;
double sum = 0;
int i;
avg = 0;
for (i=1; i < size; i++)
{
count++;
sum += data[i];
if ( data[i] > max)
{
max=data[i];
}
else if (data[i] < min)
{
min=data[i];
}
}
avg = sum/(double)count;
}
int main ()
{
double data[]={10.0,0.0,20.0,30.0};
double min,max,avg;
normalizeMinMaxAvg (data, 4, min, max, avg);
cout<<min<<" "<<max<<" "<<avg<<endl;
return 0;
}

Answer 3

Your problem is that you're not accessing your array's data. Instead you're using your iteration variable i. Basically, on your normalizeMinMaxAvg function, you should do this on your for loop:
for (i=0; i < size; i++){
//count++; - no need for it, you already have size!
sum += data[i];
if ( max > data[i]){
max = data[i];
}
if (min < data[i]){
min = data[i];
}
}
avg = sum/size;
Also you need to declare your variables min, max and avg on your main() function in order to use them when you call your normalizeMinMaxAvg function.

Answer 4

There are a couple of issues with your code. You need to understand how passing arguments by reference works in C++.
void normalizeMinMaxAvg(double data[], int size,double& min, double& max, double& avg)
normalizeMinMaxAvg doesn't return anything - note the void return type - it modifies 3 already existing double variables, so if you are going to call it form main you have to define those variables.
int main()
{
double data[]={10.0,0.0,20.0,30.0};
double min = 0, max = 0, avg = 0; //variables defined and initialized here
//Note the '= 0' on all variables, it's important else they'll have random values
normalizeMinMaxAvg(data, sizeof(data)/sizeof(data[0]), min, max, avg);
//Your function has modified min, max, and avg, so you use them here
std::cout << min << ", " << max << ", " << avg << std::endl;
return 0;
}
Your normalizeMinMaxAvg function also has problems:
void normalizeMinMaxAvg(double data[], int size,double& min, double& max, double& avg)
{
if (size <= 0) //Nothing to do. Might want to add a return error code
return;
//0 is not a sensible value for init, what if all your values are negative?
min = data[0];
max = data[0];
avg = 0;
int sum = 0;
for (i=0; i < size; i++)
{
sum += data[i];
if ( data[i] > max) { //have to access your data by data[i]
max=data[i]; //NOT i=max, you're assigning to max
}
if (data[i] < min) {
min=data[i];
}
}
avg = sum/size;
}

Answer 5

Couple things I noticed:
The values are stored in data[] so you must use data[i] in your loop to check for min, max, and to compute the average.
Also, you want to initialize min to the maximum double value so that it will be replaced by the actual minimum from the data.

Answer 6

You need to be referencing the items in the array. So it should not just simply be i, that is just a number. It should be data[i]. This will refer to the ith element of the array data.

Answer 7

Three things:
You have to define min, max, avg in your main() function before passing them on.
You can't cout << function() if it doesn't return anything.
In normalizeMinMaxAvg for loop, you access i (index) instead of data[i] (the data under index i in array data).