Program to find if a character is vowel or Consonant

Given a character ch representing an English alphabet, determine whether it is a vowel or not. Return true if ch is a vowel otherwise return false.

Examples:  

Input: ch = 'a'
Output: true
Explanation: 'a' is a vowel. So output for this test case is true.

Input: ch = 'Z'
Output: false
Explanation: 'Z' is not a vowel. So output for this test case is false.

Using Direct Character Comparison (Handling Uppercase & Lowercase) - O(1) Time O(1) Space

The Idea is to Directly compare the given character with all vowels (both lowercase and uppercase). If it matches any, return true; otherwise return false.

Algorithm:

• Take input character ch.
• Check if ch is equal to 'a', 'e', 'i', 'o', 'u' or 'A', 'E', 'I', 'O', 'U'.
• If any condition matches -> return true.
• Otherwise -> return false.

true

Time Complexity: O(1)
Auxiliary Space: O(1)

Using Bitmasking Technique - O(1) Time O(1) Space

Both lowercase and uppercase vowels share the same last 5 bits (LSBs) in their ASCII representation. This allows us to normalize any character using (ch & 0x1F) and map it to a small range of values.

We use a precomputed bitmask 0x208222, which is designed such that when it is right-shifted by the normalized value (ch & 0x1F), it produces 1 at the least significant bit for vowel positions (1, 5, 9, 15, 21), and 0 for all other characters.

Thus, by evaluating:

( 0 x 208222 >> (ch & 0 x 1F)) & 1

ASCII Values of Vowels (Lowercase and Uppercase):

Algorithm:

• Take input character ch.
• Compute (ch & 0x1F) to get last 5 bits.
• Right shift 0x208222 by this value.
• Apply & 1 to extract the result.
• If result is 1 → return true (vowel).
• Else → return false (not a vowel).

true

Time Complexity: O(1)
Auxiliary Space: O(1)