Check if the given string is vowel prime

Given a string str of lowercase English alphabets, the task is to check whether the string is a vowel prime or not. A string is said to be vowel prime if all the vowels in the string appear at only prime indices.

Examples:

Input: str = “geeksforgeeks”
Output: No
str[1] = ‘e’ is a vowel but 1 is not prime.

Input: str = “bcae”
Output: Yes
All the vowels are at prime indices i.e. 2 and 3.

Approach: Use Sieve of Eratosthenes to find all the prime numbers less than N so that every index of the string can be checked for primality. Now, if there is some non-prime index such that the character at that position is a vowel then the string is not vowel prime else it is.

Below is the implementation of the above approach:

C++

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// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
  
// Function that returns true if c is a vowel
bool isVowel(char c)
{
    if (c == 'a' || c == 'e' || c == 'i'
        || c == 'o' || c == 'u')
        return true;
    return false;
}
  
// Function that returns true if all the vowels in
// the given string are only at prime indices
bool isVowelPrime(string str, int n)
{
    // Create a boolean array "prime[0..n]" and initialize
    // all entries it as true. A value in prime[i] will
    // finally be false if i is Not a prime, else true.
    bool prime[n];
    memset(prime, true, sizeof(prime));
  
    // 0 and 1 are not prime
    prime[0] = false;
    prime[1] = false;
    for (int p = 2; p * p < n; p++) {
  
        // If prime[p] is not changed, then it is a prime
        if (prime[p] == true) {
  
            // Update all multiples of p greater than or
            // equal to the square of it
            // numbers which are multiple of p and are
            // less than p^2 are already been marked.
            for (int i = p * p; i < n; i += p)
                prime[i] = false;
        }
    }
  
    // For every character of the given string
    for (int i = 0; i < n; i++) {
  
        // If current character is vowel
        // and the index is not prime
        if (isVowel(str[i]) && !prime[i])
            return false;
    }
    return true;
}
  
// Driver code
int main()
{
    string str = "geeksforgeeks";
    int n = str.length();
  
    if (isVowelPrime(str, n))
        cout << "Yes";
    else
        cout << "No";
  
    return 0;
}

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Java

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// Java implementation of the approach
import java.util.*;
  
class GFG
{
  
// Function that returns true 
// if c is a vowel
static boolean isVowel(char c)
{
    if (c == 'a' || c == 'e' || 
        c == 'i' || c == 'o' ||
        c == 'u')
        return true;
    return false;
}
  
// Function that returns true if all the vowels in
// the given string are only at prime indices
static boolean isVowelPrime(String str, int n)
{
      
    // Create a boolean array "prime[0..n]" and 
    // initialize all entries it as true. 
    // A value in prime[i] will finally be false
    // if i is Not a prime, else true.
    boolean []prime = new boolean[n];
    Arrays.fill(prime, true);
  
    // 0 and 1 are not prime
    prime[0] = false;
    prime[1] = false;
    for (int p = 2; p * p < n; p++) 
    {
  
        // If prime[p] is not changed, 
        // then it is a prime
        if (prime[p] == true
        {
  
            // Update all multiples of p greater than or
            // equal to the square of it
            // numbers which are multiple of p and are
            // less than p^2 are already been marked.
            for (int i = p * p; i < n; i += p)
                prime[i] = false;
        }
    }
  
    // For every character of the given string
    for (int i = 0; i < n; i++) 
    {
  
        // If current character is vowel
        // and the index is not prime
        if (isVowel(str.charAt(i)) && !prime[i])
            return false;
    }
    return true;
}
  
// Driver code
public static void main(String[] args)
{
    String str = "geeksforgeeks";
    int n = str.length();
  
    if (isVowelPrime(str, n))
        System.out.println("Yes");
    else
        System.out.println("No");
}
}
  
// This code is contributed by Princi Singh

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Python3

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# Python3 implementation of the approach
  
# Function that returns true if c is a vowel
def isVowel(c):
    if (c == 'a' or c == 'e' or 
        c == 'i' or c == 'o' or 
        c == 'u'):
        return True
    return False
  
# Function that returns true if 
# all the vowels in the given string 
# are only at prime indices
def isVowelPrime(Str, n):
  
    # Create a boolean array "prime[0..n]" 
    # and initialize all entries in it as true. 
    # A value in prime[i] will finally be false 
    # if i is Not a prime, else true.
    prime = [True for i in range(n)]
  
    # 0 and 1 are not prime
    prime[0] = False
    prime[1] = False
    for p in range(2, n):
        if p * p > n:
            break
  
        # If prime[p] is not changed,
        # then it is a prime
        if (prime[p] == True):
  
            # Update all multiples of p greater than or
            # equal to the square of it
            # numbers which are multiple of p and are
            # less than p^2 are already been marked.
            for i in range(2 * p, n, p):
                prime[i] = False
  
    # For every character of the given String
    for i in range(n):
  
        # If current character is vowel
        # and the index is not prime
        if (isVowel(Str[i]) and 
            prime[i] == False):
            return False
    return True
  
# Driver code
Str= "geeksforgeeks";
n = len(Str)
  
if (isVowelPrime(Str, n)):
    print("Yes")
else:
    print("No")
  
# This code is contributed by Mohit Kumar

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C#

// C# implementation of the approach
using System;

class GFG
{

// Function that returns true
// if c is a vowel
static Boolean isVowel(char c)
{
if (c == ‘a’ || c == ‘e’ ||
c == ‘i’ || c == ‘o’ ||
c == ‘u’)
return true;
return false;
}

// Function that returns true if all the vowels in
// the given string are only at prime indices
static Boolean isVowelPrime(String str, int n)
{

// Create a boolean array “prime[0..n]” and
// initialize all entries it as true.
// A value in prime[i] will finally be false
// if i is Not a prime, else true.
Boolean []prime = new Boolean[n];
for(int i = 0; i < n; i++) prime[i] = true; // 0 and 1 are not prime prime[0] = false; prime[1] = false; for (int p = 2; p * p < n; p++) { // If prime[p] is not changed, // then it is a prime if (prime[p] == true) { // Update all multiples of p greater than // or equal to the square of it // numbers which are multiple of p and are // less than p^2 are already been marked. for (int i = p * p; i < n; i += p) prime[i] = false; } } // For every character of the given string for (int i = 0; i < n; i++) { // If current character is vowel // and the index is not prime if (isVowel(str[i]) && !prime[i]) return false; } return true; } // Driver code public static void Main(String[] args) { String str = "geeksforgeeks"; int n = str.Length; if (isVowelPrime(str, n)) Console.WriteLine("Yes"); else Console.WriteLine("No"); } } // This code is contributed by Princi Singh [tabbyending]

Output:

No


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