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

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  • Difficulty Level : Hard
  • Last Updated : 21 Jul, 2022

Given a string return all possible subsequences which start with a vowel and end with a 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 consonant
                 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 hashset.
  • Step 6: Iterate over the substring drop each character  and recur to generate all its subString

C++




// 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 consonant
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

Java




// 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);
    }
}

Python3




# Python program to generate all the subse-quence
# starting with vowel and ending with consonant.
 
# Set to store all the subsequences
st = set()
 
# Utility method to check vowel
def isVowel(c):
 
    return (c == 'a' or c == 'e' or
            c == 'i' or c == 'o' or
            c == 'u')
 
# Utility method to check consonant
def isConsonant(c):
 
    return not isVowel(c)
 
# It computes all the possible substring that
# starts with vowel and end with consonant
def subsequence(Str):
 
    global st
 
    # iterate over the entire string
    for i in range(len(Str)):
 
        # 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 j in range(len(Str) - 1,i-1,-1):
             
                # test jth character for consonant.
                if (isConsonant(Str[j])):
                 
                    # once we get a consonant add it to
                    # the hashset
                    str_sub = Str[i : i + j + 1]
                    st.add(str_sub)
 
                    # drop each character of the substring
                    # and recur to generate all subsequence
                    # of the substring
                    for k in range(1,len(str_sub)):
                     
                        sb = str_sub
                        sb = sb.replace(sb[k],"")
                        subsequence(sb)
 
# Driver Code
s = "xabcef"
subsequence(s)
 
for i in st:
    print(i,end = " ")
print()
 
# This code is contributed by shinjanpatra

C#




// C# Program to generate all the subsequence
// starting with vowel and ending with consonant.
using System;
using System.Collections.Generic;
using System.Text;
 
class Subsequence
{
 
    // Set to store all the subsequences
    static HashSet<String> st = new HashSet<String>();
 
    // 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[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.Substring(i, j -i + 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++)
                        {
                            StringBuilder sb = new StringBuilder(str_sub);
                            sb.Remove(k, 1);
                            subsequence(sb.ToString());
                        }
                    }
                }
            }
        }
    }
 
    // Utility method to check vowel
    static bool isVowel(char c)
    {
        return (c == 'a' || c == 'e' || c == 'i' || c == 'o'
                                            || c == 'u');
    }
 
    // Utility method to check consonant
    static bool isConsonant(char c)
    {
        return !isVowel(c);
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        String s = "xabcef";
        subsequence(s);
        foreach(String str in st)
            Console.Write(str + ", ");
    }
}
 
// This code is contributed by Rajput-Ji

Javascript




<script>
 
// JavaScript program to generate all the subse-quence
// starting with vowel and ending with consonant.
 
// Set to store all the subsequences
let st = new Set();
 
// Utility method to check vowel
function isVowel(c)
{
    return (c == 'a' || c == 'e' ||
            c == 'i' || c == 'o' ||
            c == 'u');
}
 
// Utility method to check consonant
function isConsonant(c)
{
    return !isVowel(c);
}
 
// It computes all the possible substring that
// starts with vowel and end with consonant
function subsequence(str)
{
    // iterate over the entire string
    for (let 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 (let 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
                    let str_sub = str.substring(i, i + j + 1);
                    st.add(str_sub);
 
                    // drop each character of the substring
                    // and recur to generate all subsequence
                    // of the substring
                    for (let k = 1; k < str_sub.length - 1; k++)
                    {
                        let sb = str_sub;
                        sb = sb.replace(sb[k],"");
                        subsequence(sb);
                    }
                }
            }
        }
    }
}
 
// Driver Code
let s = "xabcef";
subsequence(s);
 
for (let i of st)
    document.write(i," ");
document.write("</br>");
 
// This code is contributed by shinjanpatra
 
</script>

Output

ab abc abce abcef abcf abef abf ac acef acf aef af ef 

This article is contributed by Sumit Ghosh. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. 


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