check panagram.java

/*
	Check whether a string is a Panagram or not.

	Note that a string is a Panagram if it contains all the character of the alphabets ignoring the case of the alphabets  

	For example, 	str = “Abcdefghijklmnopqrstuvwxyz”
			Output: Yes
			Explanation: The given string contains all the letters from a to z (ignoring case).

			str = "AbhayChetri"
			Output: No 
			Explaination: The given string doesn't contain all the letters from a to z. 

Approach:-  1.Convert each letter of the string to the lower or upper case.
	    2.Create a frequency array to mark the frequency of each letter from a to z.
	    3.Then, traverse the frequency array and if there is any letter that is not present in the given string then print "No", otherwise print "Yes".

	Time Complexity: O(N) 
	Auxiliary Space: O(26)

*/

class Abhay {

	static int size = 26;

	// Function to check if ch is a letter
	static boolean isLetter(char ch)
	{
		if (!Character.isLetter(ch))
			return false;

		return true;
	}

	// Function to check if a string
	// contains all the letters from
	// a to z
	static boolean allLetter(String str,
							int len)
	{
		// Convert the given string
		// into lowercase
		str = str.toLowerCase();

		// Create a frequency array to
		// mark the present letters
		boolean[] present = new boolean[size];

		// Traverse for each character
		// of the string
		for (int i = 0; i < len; i++) {

			// If the current character
			// is a letter
			if (isLetter(str.charAt(i))) {

				// Mark current letter as present
				int letter = str.charAt(i) - 'a';
				present[letter] = true;
			}
		}

		// Traverse for every letter
		// from a to z
		for (int i = 0; i < size; i++) {

			// If the current character
			// is not present in string
			// then return false,
			// otherwise return true
			if (!present[i])
				return false;
		}
		return true;
	}

	// Driver Code
	public static void main(String args[])
	{

		// Given string str
		String str = "Abcdefghijklmnopqrstuvwxyz";
		int len = str.length();

		// Function Call
		if (allLetter(str, len))
			System.out.println("Yes");
		else
			System.out.println("No");
	}
}