How to Count Vowels in C++

The challenge

Return the number (count) of vowels in the given string.

We will consider a, e, i, o, u as vowels for this challenge (but not y).

The input string will only consist of lower case letters and/or spaces.

The solution in C++

Option 1:

#include <string>

using namespace std;

bool is_vowel(char c) {
  return (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');
}

int getCount(const string& inputStr) {
  return count_if(inputStr.begin(), inputStr.end(), is_vowel);
}

Option 2:

#include <string>

using namespace std;

int getCount(const string& inputStr){
  return count_if(inputStr.begin(), inputStr.end(), [](const char ch) {
      switch(ch) {
          case 'a':
          case'e':
          case'i':
          case'o':
          case'u':
              return true;
          default:
              return false;} 
     });
}

Option 3:

#include <string>

using namespace std;

int getCount(const string& inputStr){
  int num_vowels = 0;
  for( const auto &c : inputStr ) 
      if(c=='a'||c=='e'||c=='i'||c=='o'||c=='u') num_vowels++;
  return num_vowels;
}

Test cases to validate our solution

#include <ctime>
#include <cstdlib>

using namespace std;

Describe(test_cases) {
    It(test_1) {
        Assert::That(getCount("abracadabra"), Equals(5));
    }
    It(test_2) {
        Assert::That(getCount(""), Equals(0));
    }
    It(test_3) {
        Assert::That(getCount("pear tree"), Equals(4));
    }
    It(test_4) {
        Assert::That(getCount("o a kak ushakov lil vo kashu kakao"), Equals(13));
    }
    It(test_5) {
        Assert::That(getCount("tk r n m kspkvgiw qkeby lkrpbk uo thouonm fiqqb kxe ydvr n uy e oapiurrpli c ovfaooyfxxymfcrzhzohpek w zaa tue uybclybrrmokmjjnweshmqpmqptmszsvyayry kxa hmoxbxio qrucjrioli  ctmoozlzzihme tikvkb mkuf evrx a vutvntvrcjwqdabyljsizvh affzngslh  ihcvrrsho pbfyojewwsxcexwkqjzfvu yzmxroamrbwwcgo dte zulk ajyvmzulm d avgc cl frlyweezpn pezmrzpdlp yqklzd l ydofbykbvyomfoyiat mlarbkdbte fde pg   k nusqbvquc dovtgepkxotijljusimyspxjwtyaijnhllcwpzhnadrktm fy itsms ssrbhy zhqphyfhjuxfflzpqs mm fyyew ubmlzcze hnq zoxxrprmcdz jes  gjtzo bazvh  tmp lkdas z ieykrma lo  u placg x egqj kugw lircpswb dwqrhrotfaok sz cuyycqdaazsw  bckzazqo uomh lbw hiwy x  qinfgwvfwtuzneakrjecruw ytg smakqntulqhjmkhpjs xwqqznwyjdsbvsrmh pzfihwnwydgxqfvhotuzolc y mso holmkj  nk mbehp dr fdjyep rhvxvwjjhzpv  pyhtneuzw dbrkg dev usimbmlwheeef aaruznfdvu cke ggkeku unfl jpeupytrejuhgycpqhii  cdqp foxeknd djhunxyi ggaiti prkah hsbgwra ffqshfq hoatuiq fgxt goty"), Equals(168));
    }
};

Describe(Random_tests){

  int sol(const string& inputStr) {
    
    int num_vowels = 0;
    
    for (char c : inputStr)
      if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u')
        ++num_vowels;
    
    return num_vowels;
  }
  
  It(randomized_tests) {
    srand(time(0));
    
    for(int i = 0; i<41; ++i){ //generate 40 random tests
      string s;
      int n = rand()% 100 +1; //generate random length for the string
      for (int j = 0; j < n; ++j) { //generate random string from a to z, including space
        int x = rand() % 27 + 97;
        if (x == 123)
          s.push_back(32);
        else
          s.push_back(x);
      }
      Assert::That(getCount(s), Equals(sol(s)));
    }
  }
};