Question

I’m C++ begginer. I did this excercise from Deitel’s book:

Use a one-dimensional array to solve
the following problem. Read in 20
numbers, each of which is between 10
and 100, inclusive. As each number is
read, validate it and store it in the
array only if it is not a duplicate of
a number already read. After reading
all the values, display only the
unique values that the user entered.
Provide for the “worst case” in which
all 20 numbers are different. Use the
smallest possible array to solve this
problem.

Here is my code:

#include <iostream>

using namespace std;

bool compare(int arrayNum[],int arraySize,int element);

int main()
{
    const int size=20;
    int i=1;
    int num[size];
    int arrayElement;
    int counter=0;

    while(i<=20)
    {

        cin>>arrayElement;
        if(i==1)    //stores first element in array
            num[0]=arrayElement;
        //compare new element with stored elements
        //if element is not a duplicate store it in array
        else if (compare(num,size,arrayElement))
        {
            counter++;
            num[counter]=arrayElement;
        }


        i++;
    }
    //displays array elements
    for(int k=0;k<=counter;k++)
        cout<<num[k]<<endl;

    return 0;
}

//compare elements in array

bool compare(int arrayNum[],int arraySize,int element)
{
    for(int j=0;j<arraySize;j++)
    {
        if(arrayNum[j]==element)
            return false;
    }

    return true;
}

It works, but I’m not sure if I have interpreted the task correctly. I assume then I don’t have to include conditional statement for range of numbers (10 to 100 inclusive), as this will be read from the keyboard and input by me. Therefore why was this instruction included? Also at the end it says

use the smallest possible array

I assume the max size has to be 20,but I don’t think there is a way to dynamically expand array size (for example while storing new elements) as array size is const. I would appreciate if someone could help me with this. Any comments regarding code, or better solution are welcome.

Answer 1

As each number is read, validate
it and store it in the array

Emphasis mine. The text clearly says that your program has to validate the input. In other words, it has to check that the entered number is between 10 and 100, and if it is not, handle the error appropriately. So yes, you do need a conditional, although exactly what you do to handle the error is up to you.

And you’re right, since arrays aren’t dynamically resizable, the array size has to be at least 20.