Count the number of vowels occurring in all the substrings of given string

Given a string of length N of lowercase characters containing 0 or more vowels, the task is to find the count of vowels occurred in all the substrings of the given string.

Examples:

Input: str = “abc”
Output: 3



The given string “abc” contains only one vowel = ‘a’
Substrings of “abc” are = {“a”, “b”, “c”, “ab”, “bc, “abc”}
Hence, the sum of occurrences of the vowel in these strings = 3.(‘a’ occurred 3 times)

Input: str = “daceh”
Output: 16

Naive Approach: Given a string of length N, the number of substrings that can be formed=N(N+1)/2. A simple solution is for each substring, we count the occurrences of the vowels and add them to get the result. The time complexity of this approach is O(N3) which is not suitable for large values of N.

Efficient Approach: The idea is to use a prefix sum array-based technique where we store the occurrences of each character in all the substrings concatenated.

  • For the first character,

    no. of occurrences = no. of substrings starting with the first character = N.

  • For each of the following characters, we store the

    no. of substrings starting with that character + the number of substrings formed by the previous characters containing this character – the number of substrings formed by the previous characters only.

Below is the implementation of the above approach:

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ implementation of the above approach
#include <bits/stdc++.h>
using namespace std;
  
// Returns the total sum of
// occurrences of all vowels
int vowel_calc(string s)
{
    int n = s.length();
    vector<int> arr;
  
    for (int i = 0; i < n; i++) {
  
        if (i == 0)
            // No. of occurrences of 0th character
            // in all the substrings
            arr.push_back(n);
  
        else
            // No. of occurrences of the ith character
            // in all the substrings
            arr.push_back((n - i) + arr[i - 1] - i);
    }
  
    int sum = 0;
    for (int i = 0; i < n; i++)
  
        // Check if ith character is a vowel
        if (s[i] == 'a' || s[i] == 'e' || s[i] == 'i'
            || s[i] == 'o' || s[i] == 'u')
            sum += arr[i];
  
    // Return the total sum
    // of occurrences of vowels
    return sum;
}
  
// Driver code
int main()
{
    string s = "daceh";
    cout << vowel_calc(s) << endl;
  
    return 0;
}

chevron_right






                        filter_none









Java














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















// Java implementation of the above approach 


  


import java.io.*; 


import java.util.*; 


  


public class Gfg { 


  


    // Returns the total sum of 


    // occurrences of all vowels 


    static int vowel_calc(String s) 


    { 


        int n = s.length(); 


        int arr[] = new int[n]; 


  


        for (int i = 0; i < n; i++) { 


  


            if (i == 0) 


                // No. of occurrences of 0th character 


                // in all the substrings 


                arr[i] = n; 


  


            else


                // No. of occurrences of ith character 


                // in all the substrings 


                arr[i] = (n - i) + arr[i - 1] - i; 


        } 


  


        int sum = 0; 


        for (int i = 0; i < n; i++) { 


            char ch = s.charAt(i); 


            // Check if ith character is a vowel 


            if (ch == 'a' || ch == 'e' || ch == 'i'


                || ch == 'o' || ch == 'u') 


                sum += arr[i]; 


        } 


  


        // Return the total sum 


        // of occurences of vowels 


        return sum; 


    } 


  


    // Driver Code 


    public static void main(String args[]) 


    { 


        String s = "daceh"; 


        System.out.println(vowel_calc(s)); 


    } 


} 



















                        chevron_right







                        filter_none









Python3














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















# Python 3 implementation of the  


# above approach 


  


# Returns the total sum of  


# occurrences of all vowels 


def vowel_calc(s): 


    n = len(s) 


    arr = [] 


  


    for i in range(0, n, 1): 


        if (i == 0): 


              


            # No. of occurrences of 0th  


            # character in all the substrings 


            arr.append(n) 


  


        else: 


              


            # No. of occurrences of the ith  


            # character in all the substrings 


            arr.append((n - i) + arr[i - 1] - i) 


  


    sum = 0


    for i in range(0, n, 1): 


          


        # Check if ith character is a vowel 


        if (s[i] == 'a' or s[i] == 'e' or


            s[i] == 'i' or s[i] == 'o' or 


            s[i] == 'u'): 


            sum += arr[i] 


  


    # Return the total sum 


    # of occurrences of vowels 


    return sum


  


# Driver code 


if __name__ == '__main__': 


    s = "daceh"


    print(vowel_calc(s)) 


  


# This code is contributed by  


# Surendra_Gangwar 



















                        chevron_right







                        filter_none









C#














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















// C# implementation of the above approach 


   


  


using System; 


   


public class Gfg { 


   


    // Returns the total sum of 


    // occurrences of all vowels 


    static int vowel_calc(string s) 


    { 


        int n = s.Length; 


        int[] arr = new int[n]; 


   


        for (int i = 0; i < n; i++) { 


   


            if (i == 0) 


                // No. of occurrences of 0th character 


                // in all the substrings 


                arr[i] = n; 


   


            else


                // No. of occurrences of ith character 


                // in all the substrings 


                arr[i] = (n - i) + arr[i - 1] - i; 


        } 


   


        int sum = 0; 


        for (int i = 0; i < n; i++) { 


            char ch = s[i]; 


            // Check if ith character is a vowel 


            if (ch == 'a' || ch == 'e' || ch == 'i'


                || ch == 'o' || ch == 'u') 


                sum += arr[i]; 


        } 


   


        // Return the total sum 


        // of occurences of vowels 


        return sum; 


    } 


   


    // Driver Code 


    public static void Main() 


    { 


        string s = "daceh"; 


        Console.Write(vowel_calc(s)); 


    } 


} 



















                        chevron_right







                        filter_none









PHP














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















<?php 


// PHP implementation of the above approach 


  


// Returns the total sum of 


// occurrences of all vowels 


function vowel_calc($s) 


{ 


    $n = strlen($s); 


    $arr = array(); 


  


    for ($i = 0; $i < $n; $i++) 


    { 


        if ($i == 0) 


          


            // No. of occurrences of 0th character 


            // in all the substrings 


            $arr[$i] = $n; 


  


        else


          


            // No. of occurrences of ith character 


            // in all the substrings  


            $arr[$i] = ($n - $i) + $arr[$i - 1] - $i; 


        } 


  


    $sum = 0; 


    for ($i = 0; $i < $n; $i++) 


    { 


          


        // Check if ith character is a vowel 


        if ($s[$i] == 'a' || $s[$i] == 'e' ||  


            $s[$i] == 'i' || $s[$i] == 'o' || 


            $s[$i] == 'u') 


            $sum += $arr[$i]; 


        } 


  


        // Return the total sum 


        // of occurences of vowels 


        return $sum; 


    } 


  


// Driver Code 


$s = "daceh"; 


echo(vowel_calc($s)); 


  


// This code is contributed by Shivi_Aggarwal 


?> 



















                        chevron_right







                        filter_none











Output:


16





Time Complexity: O(N)



          
          
          
          

            

    

        My Personal Notes
        arrow_drop_up
    

    

        
        

            
            
        

    


Recommended Posts:
SouravAChowdhury_97
Check out this Author's contributed articles.
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on  the "Improve Article" button below.