How to find closest vowel? - c++

Question

I wrote a program that lets the user input a character. If the character is a vowel, do nothing; if the character is a consonant, find the closest vowel in the alphabet. Is there any easy way to do this?
Here's what I have for now:
char input, output;
cin >> input;
if (input == 'b'){ output = 'a'; }
else if (input == 'c'){ output = 'a'; }
else if (input == 'd'){ output = 'e'; }
else if (input == 'f'){ output = 'e'; }
else if (input == 'g'){ output = 'e'; }
else if (input == 'h'){ output = 'i'; }
else if (input == 'j'){ output = 'i'; }
else if (input == 'k'){ output = 'i'; }
else if (input == 'l'){ output = 'i'; }
else if (input == 'm'){ output = 'o'; }
else if (input == 'n'){ output = 'o'; }
else if (input == 'p'){ output = 'o'; }
else if (input == 'q'){ output = 'o'; }
else if (input == 'r'){ output = 'o'; }
else if (input == 's'){ output = 'u'; }
else if (input == 't'){ output = 'u'; }
else if (input == 'v'){ output = 'u'; }
else if (input == 'w'){ output = 'u'; }
else if (input == 'x'){ output = 'u'; }
else if (input == 'y'){ output = 'u'; }
else if (input == 'z'){ output = 'u'; }
Is there a simpler way to do this?

Answer 1

You could also use an array:
const char nearestVowels[26] = "aaaeeeeiiiiioooooouuuuuyyy";
// abcdefghijklmnopqrstuvwxyz
Then you could simply do this:
output = nearestVowels[input - 'a'];

Answer 2

Looks like you want something like this:
if (input != 'a' && input != 'e' && input != 'i' && input != 'o' && input != 'u')
{
if ('a' <= input && input <= 'c') { output = 'a'; }
else if (input <= 'g') { output = 'e'; }
else if (input <= 'l') { output = 'i'; }
else if (input <= 'r') { output = 'o'; }
else if (input <= 'z') { output = 'u'; }
}
Live On Coliru

Answer 3

It can be done like this too:
if(input>='a'&&input<='z'){
if(input<='c')output='a';
else if(input<='g')output='e';
else if(input<='l')output='i';
else if(input<='r')output='o';
else if(input<='z')output='u';
}
The first if makes sure that no input other than a~z are fed into output.

Answer 4

There are very many ways to do this, perhaps the most concise (albeit ugly) is:
const char* p = strchr(input, "bacadefegehijikilimonopoqorosutuvuwuxuyuzu");
output = (p && *p) ? p[1] : input;
This works by seeking a char* to input in that string literal, then if found it returns the following character. It won't crash for any character code 0-255, but if you input a vowel it will find it in the string and return the following consonant - if that's a problem, it's probably better to use the following...
Have two arrays - one of consonants and another of vowels, and if you find input in the former get the vowel from the same index in the latter.
Yet another way is to use a std::map:
std::map<char, char> m { { 'b', 'a' }, {'c', 'a' } etc... };
if (auto i = m.find(input))
output = *i;
else
output = input;
switch is a bit more verbose than the above, but will likely give the fastest performance (but do measure if you care).

Answer 5

switch would be simpler:
switch (input)
{
case 'b':
case 'c':
output = 'a';
break;
case 'd':
case 'f':
case 'g':
output = 'e';
break;
...
etc.
}

Answer 6

This feels more generic:
Get the ASCII value of the input
Substract each vowels's ASCII value as its distance and store (vowel, distance) in a list
Sort the list
Get its first pair's key (the vowel)
#include <iostream>
#include <algorithm>
#include <vector>
#include <cmath>
using namespace std;
bool compare(const pair<char, int>& a, const pair<char, int>& b)
{
return a.second < b.second;
}
int main()
{
char vowels[] = { 'a', 'e', 'i', 'o', 'u' };
char input;
//std::cin >> input;
input = 'r';
vector<pair<char, int>> distances;
for (char& vowel : vowels)
{
distances.push_back(make_pair(vowel, abs(input - vowel)));
}
sort(distances.begin(), distances.end(), compare);
pair<char, int> nearest = distances.front();
if (nearest.second > 0)
{
cout << nearest.first;
}
}

Answer 7

Here's one I made in Java, it's not assigned statically and supports lower and upper case letters.
public static char closestVowel(char character) {
int value = (int) character;
if(character == 'z' || character == 'Z')
return (char) (value - 25);
if(isVowel(character)) {
return character;
} else {
return closestVowel((char) (value - 1));
}
}
public static boolean isVowel(char character) {
return "aeiouAEIOU".indexOf(character) >= 0;
}