Update Pangram.java

src/main/java/com/thealgorithms/strings/Pangram.java

@@ -3,52 +3,55 @@
 import java.util.HashSet;
 
 /**
+ * Checks if a given string is a Pangram (a sentence containing every letter of the alphabet at least once).
  * Wikipedia: https://en.wikipedia.org/wiki/Pangram
  */
 public final class Pangram {
+
  private Pangram() {
  }
 
  /**
- * Test code
+ * Main method to test all pangram-checking methods.
  */
  public static void main(String[] args) {
  assert isPangram("The quick brown fox jumps over the lazy dog");
  assert !isPangram("The quick brown fox jumps over the azy dog"); // L is missing
  assert !isPangram("+-1234 This string is not alphabetical");
  assert !isPangram("\u0000/\\");
+ assert isPangramUsingBitwise("The quick brown fox jumps over the lazy dog");
+ assert !isPangramUsingBitwise("Hello, World!");
  }
 
  /**
- * Checks if a String is considered a Pangram
+ * Checks if a String is a Pangram using a HashSet to track unique characters.
  *
  * @param s The String to check
  * @return {@code true} if s is a Pangram, otherwise {@code false}
  */
- // alternative approach using Java Collection Framework
  public static boolean isPangramUsingSet(String s) {
- HashSet<Character> alpha = new HashSet<>();
- s = s.trim().toLowerCase();
- for (int i = 0; i < s.length(); i++) {
- if (s.charAt(i) != ' ') {
- alpha.add(s.charAt(i));
+ HashSet<Character> uniqueChars = new HashSet<>();
+ s = s.toLowerCase();
+ for (char c : s.toCharArray()) {
+ if (c >= 'a' && c <= 'z') {
+ uniqueChars.add(c);
  }
  }
- return alpha.size() == 26;
+ return uniqueChars.size() == 26;
  }
 
  /**
- * Checks if a String is considered a Pangram
+ * Checks if a String is a Pangram by tracking occurrences of each letter in an array.
  *
  * @param s The String to check
  * @return {@code true} if s is a Pangram, otherwise {@code false}
  */
  public static boolean isPangram(String s) {
  boolean[] lettersExisting = new boolean[26];
+ s = s.toLowerCase();
  for (char c : s.toCharArray()) {
- int letterIndex = c - (Character.isUpperCase(c) ? 'A' : 'a');
- if (letterIndex >= 0 && letterIndex < lettersExisting.length) {
- lettersExisting[letterIndex] = true;
+ if (c >= 'a' && c <= 'z') {
+ lettersExisting[c - 'a'] = true;
  }
  }
  for (boolean letterFlag : lettersExisting) {
@@ -60,7 +63,7 @@ public static boolean isPangram(String s) {
  }
 
  /**
- * Checks if a String is Pangram or not by checking if each alhpabet is present or not
+ * Checks if a String is a Pangram by checking each letter in the alphabet individually.
  *
  * @param s The String to check
  * @return {@code true} if s is a Pangram, otherwise {@code false}
@@ -69,12 +72,32 @@ public static boolean isPangram2(String s) {
  if (s.length() < 26) {
  return false;
  }
- s = s.toLowerCase(); // Converting s to Lower-Case
+ s = s.toLowerCase();
  for (char i = 'a'; i <= 'z'; i++) {
  if (s.indexOf(i) == -1) {
- return false; // if any alphabet is not present, return false
+ return false; // if any alphabet is missing, return false
  }
  }
  return true;
  }
+
+ /**
+ * Optimized Pangram check using Bitwise operations.
+ * Each bit in a 32-bit integer represents a unique letter from 'a' to 'z'.
+ *
+ * @param s The String to check
+ * @return {@code true} if s is a Pangram, otherwise {@code false}
+ */
+ public static boolean isPangramUsingBitwise(String s) {
+ int checker = 0;
+ s = s.toLowerCase();
+ for (char c : s.toCharArray()) {
+ if (c >= 'a' && c <= 'z') {
+ int bitIndex = c - 'a';
+ checker |= (1 << bitIndex);
+ }
+ }
+ // If all 26 bits are set, checker will equal 0b11111111111111111111111111 (26 ones)
+ return checker == (1 << 26) - 1;
+ }
 }