CODEWITHSUNDEEP
c++
alex Hexan
alex Hexan

Reputation: 155

How to check for letter occurrences in a string?

I am a complete c++ beginner and this knowledge sort of comes from other languages I tried to learn. The code below is a function from a morse code translator that I am trying to build and I am pretty sure that this is not even close to "a good way" of doing it. My question is, how would I make the program look through the the string that the user typed in and change each occurrence of the letter to morse.

string  ReplaceAll(std::string str, const std::string& from, const std::string& to){
size_t start_pos = 0;
while ((start_pos = str.find(from, start_pos)) != std::string::npos) {
    str.replace(start_pos, from.length(), to);
    start_pos += to.length(); // Handles case where 'to' is a substring of 'from'
}
return str;}


void Translate(string s) {
static string s2 = ReplaceAll(string(s), std::string("a"), std::string(".- "));
static string s3 = ReplaceAll(string(s2), std::string("b"), std::string("-... "));
static string s4 = ReplaceAll(string(s3), std::string("c"), std::string("-.-. "));
static string s5 = ReplaceAll(string(s4), std::string("d"), std::string("-.. "));
static string s6 = ReplaceAll(string(s5), std::string("e"), std::string(". "));
static string s7 = ReplaceAll(string(s6), std::string("f"), std::string("..-. "));
static string s8 = ReplaceAll(string(s7), std::string("g"), std::string("--. "));
static string s9 = ReplaceAll(string(s8), std::string("h"), std::string(".... "));
static string s10 = ReplaceAll(string(s9), std::string("i"), std::string(".. "));
static string s11 = ReplaceAll(string(s10), std::string("j"), std::string(".--- "));
static string s12 = ReplaceAll(string(s11), std::string("k"), std::string("-.- "));
static string s13 = ReplaceAll(string(s12), std::string("l"), std::string(".-.. "));
static string s14 = ReplaceAll(string(s13), std::string("m"), std::string("-- "));
static string s15 = ReplaceAll(string(s14), std::string("n"), std::string("-. "));
static string s16 = ReplaceAll(string(s15), std::string("o"), std::string("--- "));
static string s17 = ReplaceAll(string(s16), std::string("p"), std::string(".--. "));
static string s18 = ReplaceAll(string(s17), std::string("q"), std::string("--.- "));
static string s19 = ReplaceAll(string(s18), std::string("r"), std::string(".-. "));
static string s20 = ReplaceAll(string(s19), std::string("s"), std::string("... "));
static string s21 = ReplaceAll(string(s20), std::string("t"), std::string("- "));
static string s22 = ReplaceAll(string(s21), std::string("u"), std::string("..- "));
static string s23 = ReplaceAll(string(s22), std::string("v"), std::string("...- "));
static string s24 = ReplaceAll(string(s23), std::string("w"), std::string(".-- "));
static string s25 = ReplaceAll(string(s24), std::string("x"), std::string("-..- "));
static string s26 = ReplaceAll(string(s25), std::string("y"), std::string("-.-- "));
static string s27 = ReplaceAll(string(s26), std::string("z"), std::string("--.. "));

cout << s27 << endl;

}

Upvotes: 2

Views: 129

Answers (2)

R1tschY
R1tschY

Reputation: 3212

It is a better solution to build a std::map with the replacements and go through all the characters and build a new string. With your solution characters like ., -, ! are in the result.

#include <iostream>
#include <map>

typedef std::map<char, const char*> Replacements;

std::string Translate(const Replacements& r, std::string s) 
{
    std::string result;
    result.reserve(s.size() * 5); // optional: reserve guessed number of elements for new string

    // for every element of the string
    for (char c : s)
    {
        // search for replacement
        Replacements::const_iterator iter = r.find(c);
        if (iter != r.end())
        {
            // found replacement
          result += iter->second;
          result.push_back(' ');
        }       
    }

    return result;
}


int main() 
{
    Replacements morse_code;
    morse_code['a'] = ".-";
    morse_code['b'] = "-...";
    morse_code['c'] = "-.-.";
    // ...

    std::string in; 
    if (std::cin >> in)
        std::cout << Translate(morse_code, in) << '\n';
}

Upvotes: 2

Sam Varshavchik
Sam Varshavchik

Reputation: 118330

This is a wrong approach. Instead of trying to replace the contents of the string, it's much easier to simply create a new string:

std::string TranslateAll(const std::string &s)
{
    std::ostringstream o;

    for (char c:s)
        o << Translate(c);

    return o.str();
}

Now, you can write a much simpler

const char *Translate(char c)

All that it does is take a single character as a parameter, and returns its morse code, as a simple character string.

Much easier.

Upvotes: 0

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