Print all Subsequences of String which Start with Vowel and End with Consonant.

Given a string return all possible subsequences which start with vowel and end with consonant. A String is a subsequence of a given String, that is generated by deleting some character of a given string without changing its order.
Examples:

Input : 'abc'
Output : ab, ac, abc

Input : 'aab'
Output : ab, aab

Question Source: Yatra.com Interview Experience | Set 7

Explanation of the Algorithm: 



Step 1: Iterate over the entire String
Step 2: check if the ith character for vowel
Step 3: If true iterate the string from the end,
        if false move to next iteration
Step 4: check the jth character for consonent
        if false move to next iteration 
        if true perform the following 
Step 5: Add the substring starting at index i and
        ending at index j to the hastset.
Step 6: Iterate over the substring drop each character 
        and recur to generate all its subString

C++

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// C++ program to generate all the subse-quence
// starting with vowel and ending with consonant.
#include <bits/stdc++.h>
using namespace std;
  
// Set to store all the subsequences
set<string> st;
  
// Utility method to check vowel
bool isVowel(char c)
{
    return (c == 'a' or c == 'e' or
            c == 'i' or c == 'o' or
            c == 'u');
}
  
// Utility method to check consonant
bool isConsonant(char c)
{
    return !isVowel(c);
}
  
// It computes all the possible substring that
// starts with vowel and end with consonent
void subsequence(string str)
{
    // iterate over the entire string
    for (int i = 0; i < str.length(); i++)
    {
        // test ith character for vowel
        if (isVowel(str[i]))
        {
            // if the ith character is vowel
            // iterate from end of the string
            // and check for consonant.
            for (int j = str.length() - 1; j >= i; j--)
            {
                // test jth character for consonant.
                if (isConsonant(str[j]))
                {
                    // once we get a consonant add it to
                    // the hashset
                    string str_sub = str.substr(i, j + 1);
                    st.insert(str_sub);
  
                    // drop each character of the substring
                    // and recur to generate all subsequence
                    // of the substring
                    for (int k = 1; k < str_sub.length() - 1; k++)
                    {
                        string sb = str_sub;
                        sb.erase(sb.begin() + k);
                        subsequence(sb);
                    }
                }
            }
        }
    }
}
  
// Driver Code
int main()
{
    string s = "xabcef";
    subsequence(s);
  
    for (auto i : st)
        cout << i << " ";
    cout << endl;
  
    return 0;
}
  
// This code is contributed by
// sanjeev2552

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// Java Program to generate all the subsequence 


// starting with vowel and ending with consonant. 


import java.util.HashSet; 


  


public class Subsequence { 


  


    // Set to store all the subsequences 


    static HashSet<String> st = new HashSet<>(); 


  


    // It computes all the possible substring that 


    // starts with vowel and end with consonent 


    static void subsequence(String str) 


    { 


        // iterate over the entire string 


        for (int i = 0; i < str.length(); i++) { 


          


            // test ith character for vowel 


            if (isVowel(str.charAt(i))) { 


          


                // if the ith character is vowel 


                // iterate from end of the string 


                // and check for consonant. 


                for (int j = (str.length() - 1); j >= i; j--) { 


                      


                    // test jth character for consonant. 


                    if (isConsonant(str.charAt((j)))) { 


                      


                        // once we get a consonant add it to  


                        // the hashset 


                        String str_sub = str.substring(i, j + 1); 


                        st.add(str_sub); 


  


                        // drop each character of the substring 


                        // and recur to generate all subsequence 


                        // of the substring 


                        for (int k = 1; k < str_sub.length() - 1; k++) { 


                            StringBuffer sb = new StringBuffer(str_sub); 


                            sb.deleteCharAt(k); 


                            subsequence(sb.toString()); 


                        } 


                    } 


                } 


            } 


        } 


    } 


  


    // Utility method to check vowel 


    static boolean isVowel(char c) 


    { 


        return (c == 'a' || c == 'e' || c == 'i' || c == 'o'


                                              || c == 'u'); 


    } 


  


    // Utility method to check consonant 


    static boolean isConsonant(char c) 


    { 


        return !isVowel(c); 


    } 


  


    // Driver code 


    public static void main(String[] args) 


    { 


        String s = "xabcef"; 


        subsequence(s); 


        System.out.println(st); 


    } 


} 



















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Output:


[ef, ab, ac, aef, abc, abf, af, acf, abcef, abcf, acef, abef]



This article is contributed by Sumit Ghosh. 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.


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