Count of substrings containing exactly K vowels

Given string str containing both uppercase and lowercase letters, and an integer K. The task is to find the count of substrings containing exactly K vowels (maybe repetitive).

Examples:

Input: str = “aeiou”, K = 2
Output: 4
Explanation: The substrings are “ae”, “ei”, “io”, “ou”.

Input: str = “TrueGeek”, K = 3
Output: 5
Explanation: All such possible substrings are:
“TrueGe”, “rueGe”, “ueGe”, “eGee”, “eGeek”.

Approach: To solution of this problem is based on greedy approach. Generate all substrings and for each substring check the count of vowels. Follow the steps mentioned below.

• Generate all the substrings. For each substring do the following
  • Store the count of occurrences of vowels.
  • Check if a new character in the substring is a vowel or not.
  • If it is a vowel, increment count of vowels found
  • Now for each substring, if the count of vowels is K, increment the final count.
• Return the final count as the required answer at the end.

Below is the implementation of the above code.

C++

// C++ code to implement above approach
#include <bits/stdc++.h>
using namespace std;

#define MAX 128

// Function to check whether
// a character is vowel or not
bool isVowel(char x)
{
    return (x == 'a' || x == 'e' ||
            x == 'i' || x == 'o' || x == 'u'
            || x == 'A' || x == 'E' ||
            x == 'I' || x == 'O' || x == 'U');
}

// Function to find the count of
// substring with k vowels
int get(string str, int k)
{

    int n = str.length();

    // Stores the count of
    // substring with K vowels
    int ans = 0;

    // Consider all substrings
    // beginning with str[i]
    for (int i = 0; i < n; i++) {
        int count = 0;

        // Consider all substrings
        // between [i, j]
        for (int j = i; j < n; j++) {

            // If this is a vowel, for this
            // substring, increment count.
            if (isVowel(str[j])) {
                count++;
            }

            // If vowel count becomes k,
            // then increment final count.
            if (count == k) {
                ans++;
            }

            if (count > k)
                break;
        }
    }
    return ans;
}

// Driver code
int main(void)
{
    string s = "aeiou";
    int K = 2;
    cout << get(s, K);
    return 0;
}

Java

// Java code to implement above approach
class GFG
{

  static final int MAX = 128;

  // Function to check whether
  // a character is vowel or not
  static boolean isVowel(char x)
  {
    return (x == 'a' || x == 'e' ||
            x == 'i' || x == 'o' || x == 'u'
            || x == 'A' || x == 'E' ||
            x == 'I' || x == 'O' || x == 'U');
  }

  // Function to find the count of
  // subString with k vowels
  static int get(String str, int k)
  {

    int n = str.length();

    // Stores the count of
    // subString with K vowels
    int ans = 0;

    // Consider all subStrings
    // beginning with str[i]
    for (int i = 0; i < n; i++) {
      int count = 0;

      // Consider all subStrings
      // between [i, j]
      for (int j = i; j < n; j++) {

        // If this is a vowel, for this
        // subString, increment count.
        if (isVowel(str.charAt(j))) {
          count++;
        }

        // If vowel count becomes k,
        // then increment final count.
        if (count == k) {
          ans++;
        }

        if (count > k)
          break;
      }
    }
    return ans;
  }

  // Driver code
  public static void main(String[] args)
  {
    String s = "aeiou";
    int K = 2;
    System.out.print(get(s, K));
  }
}

// This code is contributed by 29AjayKumar

Python3

# python code to implement above approach
MAX = 128

# Function to check whether
# a character is vowel or not
def isVowel(x):

    return (x == 'a' or x == 'e' or
            x == 'i' or x == 'o' or x == 'u'
            or x == 'A' or x == 'E' or
            x == 'I' or x == 'O' or x == 'U')

# Function to find the count of
# substring with k vowels
def get(str, k):

    n = len(str)

    # Stores the count of
    # substring with K vowels
    ans = 0

    # Consider all substrings
    # beginning with str[i]
    for i in range(0, n):
        count = 0

        # Consider all substrings
        # between [i, j]
        for j in range(i, n):

            # If this is a vowel, for this
            # substring, increment count.
            if (isVowel(str[j])):
                count += 1

            # If vowel count becomes k,
            # then increment final count.
            if (count == k):
                ans += 1

            if (count > k):
                break

    return ans

# Driver code
if __name__ == "__main__":

    s = "aeiou"
    K = 2
    print(get(s, K))

# This code is contributed by rakeshsahni

C#

// C# code to implement above approach
using System;
class GFG {

  // Function to check whether
  // a character is vowel or not
  static bool isVowel(char x)
  {
    return (x == 'a' || x == 'e' || x == 'i' || x == 'o'
            || x == 'u' || x == 'A' || x == 'E'
            || x == 'I' || x == 'O' || x == 'U');
  }

  // Function to find the count of
  // substring with k vowels
  static int get(string str, int k)
  {

    int n = str.Length;

    // Stores the count of
    // substring with K vowels
    int ans = 0;

    // Consider all substrings
    // beginning with str[i]
    for (int i = 0; i < n; i++) {
      int count = 0;

      // Consider all substrings
      // between [i, j]
      for (int j = i; j < n; j++) {

        // If this is a vowel, for this
        // substring, increment count.
        if (isVowel(str[j])) {
          count++;
        }

        // If vowel count becomes k,
        // then increment final count.
        if (count == k) {
          ans++;
        }

        if (count > k)
          break;
      }
    }
    return ans;
  }

  // Driver code
  public static void Main()
  {
    string s = "aeiou";
    int K = 2;
    Console.WriteLine(get(s, K));
  }
}

// This code is contributed by ukasp.

Javascript

<script>
   // JavaScript code for the above approach

   let MAX = 128

   // Function to check whether
   // a character is vowel or not
   function isVowel(x) {
     return (x == 'a' || x == 'e' ||
       x == 'i' || x == 'o' || x == 'u'
       || x == 'A' || x == 'E' ||
       x == 'I' || x == 'O' || x == 'U');
   }

   // Function to find the count of
   // substring with k vowels
   function get(str, k) {

     let n = str.length;

     // Stores the count of
     // substring with K vowels
     let ans = 0;

     // Consider all substrings
     // beginning with str[i]
     for (let i = 0; i < n; i++) {
       let count = 0;

       // Consider all substrings
       // between [i, j]
       for (let j = i; j < n; j++) {

         // If this is a vowel, for this
         // substring, increment count.
         if (isVowel(str[j])) {
           count++;
         }

         // If vowel count becomes k,
         // then increment final count.
         if (count == k) {
           ans++;
         }

         if (count > k)
           break;
       }
     }
     return ans;
   }

   // Driver code
   let s = "aeiou";
   let K = 2;
   document.write(get(s, K));

 // This code is contributed by Potta Lokesh
 </script>

Output

4

Time Complexity: O(N²) where N is the length of the string.
Auxiliary Space: O(1)