How to remove consonants from a string? [closed] - c++

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Here is my code:
#include <iostream>
#include <string>
#include<bits/stdc++.h>
using namespace std;
int main()
{
int n;
cin >> n;
while(n--)
{
string str;
char a[] = {'a','e','i','o','u','A','E','I','O','U'};
getline(cin, str);
for(int i=0 ;i<str.length(); i++)
{
for(int j=0; j<10; j++)
{
if(str[i]==a[j])
{
cout << str[i];
}
}
}
cout << "\n";
}
return 0;
}
Test cases are :
HmlMqPhBfaVokhR
wdTSFuI
IvfHOSNv
I am not removing anything but I am printing only vowels. But, some test cases didn't pass. Maybe this code doesn't work on multiple test cases.

Answer 1

Try this for proper console in :
int main()
{
int n;
std::cin >> n;
std::cin.ignore(); // fix
/* remaining code */
return 0;
}
> To find the vowels in a string
On way of finding the vowels in a string is using a std::binary_search each character of the given string in a vowel table.
Make a sorted array of char s of all vowels(i.e. vowels array).
For each char of the input string, std::binary_search in the
vowels array.
If std::binary_search returns true(meaning the char is an vowel), print the char of the string.
Following is the example code! (See live online)
#include <iostream>
#include <string>
#include <algorithm> // std::for_each, std::binary_search, std::sort
#include <array> // std::array
int main()
{
std::array<char, 10> a{ 'a','e','i','o','u','A','E','I','O','U' };
std::sort(a.begin(), a.end()); // need sorted array for std::binary_search
const std::string str{ "HmlMqPhBfaVokhR wdTSFuI IvfHOSNv" };
std::for_each(str.cbegin(), str.cend(), [&](const char str_char)
{
if (std::binary_search(a.cbegin(), a.cend(), str_char))
std::cout << str_char << " ";
});
return 0;
}
Output:
a o u I I O
> To remove the vowels from a string
Use erase-remove idiom as follows(till c++17†).
Make a sorted array of char s of all vowels(i.e. vowels array).
Using std::remove_if, collect the iterators pointing to the characters, which are vowels. A lambda function can be used as the predicate for std::remove_if, where the std::binary_search is used to check the char in the string exists in the vowels array.
Using std::string::erase, erase all the collected characters(i.e. vowels) from the string.
Following is an example code! (See live online)
#include <iostream>
#include <string>
#include <algorithm> // std::sort, std::binary_search, std::remove_if
#include <array> // std::array
int main()
{
std::array<char, 10> a{ 'a','e','i','o','u','A','E','I','O','U' };
std::sort(a.begin(), a.end()); // need sorted array for std::binary_search
std::string str{ "Hello World" };
// lambda(predicate) to check the `char` in the string exist in vowels array
const auto predicate = [&a](const char str_char) -> bool {
return std::binary_search(a.cbegin(), a.cend(), str_char);
};
// collect the vowels
const auto vowelsToRemove = std::remove_if(str.begin(), str.end(), predicate);
// erase the collected vowels using std::string::erase
str.erase(vowelsToRemove, str.end());
std::cout << str << "\n";
return 0;
}
Output:
Hll Wrld
† Since c++20, one can use std::erase_if for this, which would be less error prone than the the above one. (See online live using GCC 9.2)
#include <iostream>
#include <string> // std::string, std::erase_if
#include <array> // std::array
int main()
{
std::array<char, 10> a{ 'a','e','i','o','u','A','E','I','O','U' };
std::sort(a.begin(), a.end()); // need sorted array for std::binary_search
std::string str{ "Hello World" };
// lambda(predicate) to check the `char` in the string exist in vowels array
const auto predicate = [&a](const char str_char) -> bool {
return std::binary_search(a.cbegin(), a.cend(), str_char);
};
std::erase_if(str, predicate); // simply erase
std::cout << str << "\n";
return 0;
}
> To remove the consonants from a string
To remove the consonants from the given string, in the above predicate negate the result of std::binary_search. (See live online)
const auto predicate = [&a](const char str_char) -> bool {
return !std::binary_search(a.cbegin(), a.cend(), str_char);
// ^^ --> negate the return
};
As side notes,
Avoid the #include<bits/stdc++.h> Read more: Why should I not #include <bits/stdc++.h>?
Do not practice with using namespace std; Read more: Why is "using namespace std;" considered bad practice?

Answer 2

Apart from the std::getline problem already answered:
for(int i=0 ;i<str.length(); i++)
{
for(int j=0; j<10; j++)
{
if(str[i] == a[j])
{
// this is the one you do NOT want to print...
// cout<<str[i];
// skip instead:
goto SKIP;
}
}
std::cout << str[i]; // output the one NOT skipped...
SKIP: (void)0;
}
OK, don't want to start any discussion about usage of goto, there are many ways to avoid it, e. g. by packing the inner for loop into a separate (inline) function. You can have it easier, though, as there already exists such a function; code gets even easier with a range-based for loop:
for(auto c : str)
{
if(!strchr("aeiouAEIOU", c))
{
std::cout << c;
}
}
strchr (from cstring) returns a pointer to the first character in the string equal to the reference character - or nullptr if not found...
To really remove the vowels from the string in a modern C++ way, consider this:
str.erase(std::remove_if(
str.begin(), str.end(),
[](char c) { return strchr("aeiouAEIOU", c) != nullptr; }
), str.end());

Answer 3

Your code probably should looks like (please see comments inline):
#include <iostream>
#include <string>
using namespace std;
int main() {
string vowels = "aeiouAEIOU";
int n;
cin>>n; // assume this stands for line count
while(n-- >= 0)
{
string str, result;
getline(cin, str);
for(int i=0 ;i<str.length(); i++)
{
if (vowels.find(str[i]) != std::string::npos)
result += str[i]; // add character to result if it is not consonant
}
cout<<result<<"\n"; // print result
}
return 0;
}