Count how many and what letters contains text

Question

I need to count how many and what letters contains entered text. (take in account case)

I`ve already done similar task with counting numbers in text:


int main()
{
    char text[255];
    int count[10] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
    cin.getline(text, 255);

    int i = 0;
    while (text[i] != '\0')
    {
        switch (text[i])
        {
        case '0': ++count[0];
            break;
        case '1': ++count[1];
            break;
        case '2': ++count[2];
            break;
        case '3': ++count[3];
            break;
        case '4': ++count[4];
            break;
        case '5': ++count[5];
            break;
        case '6': ++count[6];
            break;
        case '7': ++count[7];
            break;
        case '8': ++count[8];
            break;
        case '9': ++count[9];
            break;
        }
        ++i;
    }

    for (int i = 0; i < 10; i++)
    {
        cout << endl << '[' << i << "] = " << count[i];
    }

}

But I wonder if there is a way to do it without writing 52 cases for both uppercase and lowercase letters. I guess I need to use ASCII table, but I cant put it all together.

`std::string text;` , `std::unordered_map count;` and that's it, problem solved — pptaszni, Feb 21 '23 at 14:33
*But I wonder if there is a way to do it without writing 52 cases for both uppercase and lowercase letters.* -- Not only will a map allow 52 cases, but any amount of separate characters. What if the language being used is not English? — PaulMcKenzie, Feb 21 '23 at 14:34
BTW, exact dupe: https://stackoverflow.com/a/38697323/4165552 — pptaszni, Feb 21 '23 at 14:35
I'm curious, why map over unordered_map? My goto for something like this is unordered_map. — sweenish, Feb 21 '23 at 14:44
@sweenish I would guess it's because the code provided has the results sorted...albeit they are numbers so that's a given. — Casey, Feb 21 '23 at 14:58

Vlad from Moscow · Accepted Answer · 2023-02-21T14:57:25.977

2

The simplest way is to use standard C function isalpha and standard container std::map<char, size_t>

For example

#include <map>
#include <cctype>

//...

std::map<char, size_t> alpha;

for ( const char *p = text; *p; ++p )
{
    if ( std::isalpha( ( unsigned char )*p ) )
    {
       ++alpha[*p];
    }
}

for ( const auto &item : alpha )
{
    std::cout << item.first << ": " << item.second << '\n';
}

Together with counting letters you can count digits. Just change the first for loop the following way

for ( const char *p = text; *p; ++p )
{
    if ( std::isalpha( ( unsigned char )*p ) || std::isdigit( ( unsigned char )*p ) )
    {
       ++alpha[*p];
    }
}

edited Feb 21 '23 at 14:57

answered Feb 21 '23 at 14:38

Vlad from Moscow

301,070
26
186
335

Question is tagged c++, why provide a C-based solution? – Casey Feb 21 '23 at 14:57
1

@Casey And where do you have seen a C solution?:) It is because he is using a character array instead of std::string? Character arrays are C++ objects.:) – Vlad from Moscow Feb 21 '23 at 14:58

Count how many and what letters contains text

1 Answers1