Retrieving a variable from an array

Question

Ok so the problem I am having is that I have an array that contains 27 characters and I need to write a function to display a specific character 0 - 25 based on a user input.

The array is a constant string:

const string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

And the idea is that a user enters a value between 1 and 25 (int value) which then displays the cosponsoring letter in the array. I doing this by using:

cout << ALPHABET[value];

My questions are is this an appropreate way to create an array and am I able to retrieve a value from an array this way.

const string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

int main()
{
    int value; //Variable defining user entered value
    cout << "Please enter a number between 0-25." << endl;
    cin >> value;
    if (value > 25) //If statement to display "-1" if number entered is past "Z"
        cout << "-1" << endl;
    else
        cout << ALPHABET[value];

    return 0;
}

Assuming by string you mean std::string, you haven't really created an array. You've created an object that that allows array-like access. — Michael Albers
– Michael Albers, Commented Apr 19, 2016 at 3:50
Step 1: Write code. Step 2: Fix errors. Step 3: Post questions on Stack Overflow for errors you can't fix. You seem to be at step 1, come back when you get to 3. — user657267
– user657267, Commented Apr 19, 2016 at 3:51
If the "array" is always going to contain the entire alphabet, then why not take the user's value (0-25) and just do 'A' + value? — paddy
– paddy, Commented Apr 19, 2016 at 3:55
@ChrisBritt Because the "" are included in the string and your right it should be 1 - 26 — Johnapples
– Johnapples, Commented Apr 19, 2016 at 3:58

Andreas DM · Accepted Answer · 2016-04-19 14:46:45Z

1

My questions are is this an appropreate way to create an array and am I able to retrieve a value from an array this way.

Although it works to use a string:

int main()
{
    const string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    int num = -1;
    while (num < 0 || num > 25) {
        cout << "Enter number (0 - 25): ";
        cin >> num;
    }

    cout << ALPHABET[num] << '\n';
}

I like to use a std::vector for containing a sequence of elements:

vector<char> ALPHABET(26);
iota(begin(ALPHABET), end(ALPHABET), 'A');

edited Apr 19, 2016 at 14:46

answered Apr 19, 2016 at 4:02

Andreas DM

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2 Comments

Johnapples Over a year ago

I have updated with my entire code to add some clarity I regards to the input and outputs. It builds fine without errors it just doesn't do what I need it to.

underscore_d Over a year ago

What possible advantage does a vector have over a string or a normal array? I can only think of drawbacks. Look at the definition length, for one. I know we like to recommend vector as a default, but surely not for everything.

Cahelle · Accepted Answer · 2016-04-19 12:14:21Z

Maybe this is what you want to do. Which includes a right way to create an array.

#include <iostream>

char ALPHABET[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '\0' }; 
//the \0 means the end of the array of characters a.k.a. a string

int main()
{
    int value; //Variable defining user entered value
    std::cout << "Please enter a number between 0-25." << std::endl;
    std::cin >> value;

    if (value > 25 || value < 0) //If statement to display "-1" if number entered is past "Z"
        std::cout << "-1" << std::endl;
    else
        std::cout << ALPHABET[value];

return 0;
}

(There are more ways to create an array) Like "char ALPHABET[26] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '\0' };

The 26 means there can NOT be more than 26 characters in this array.

If you're confused about me not using "using namespace std;" and instead "std::", if you have two namespaces with "cout" or "endl" in them the program won't know which one you want to use.

So if you want to make sure it is from the right namespace, use the name of the namespace and two colons.

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