What is the complexity of my vowel_remove in string? Is there any faster way?

[lukeahn]

This is a simple code that removes vowel. What is the complexity of my code (Big-O) and is there a better way to do it? Thanks


int main()
{
// char *text;
// text = new char[];
string a = "remove vowels";
string b = a;
int index = 0;
for (int i = 0; i < a.length(); i++)
{
cout << a[i] << endl;
if (a[i] != 'a' && a[i] != 'e' && a[i] != 'i' && a[i] != 'o' && a[i] != 'u')
{
b[index] = a[i];
index++;
}

}
b.resize(index);
cout << b << endl;;

// delete[] text;

system("pause");
return 0;

}

[MiiNiPaa]

What is the complexity of my code (Big-O)

Linear: O(n)

there a better way to do it?

Use standard library:

//Variant 1 Modifying original string
#include <iostream>
#include <string>
#include <algorithm>

int main()
{
    std::string a = "remove vowels";
    auto is_vowel = [](char c){return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';};
    a.erase(std::remove_if(a.begin(), a.end(), is_vowel), a.end());
    std::cout << a;
}

//Variant 2 Copying results to new string
#include <iostream>
#include <string>
#include <algorithm>

int main()
{
    std::string a = "remove vowels";
    auto is_not_vowel = [](char c)
        {return c != 'a' && c != 'e' && c != 'i' && c != 'o' && c != 'u';};
    std::string b;
    std::copy_if(a.begin(), a.end(), std::back_inserter(b), is_not_vowel);
    std::cout << b;
}