Coding Exercises Day 2 (Problem #4)

Problem:
Given two strings, determine if one is a permutation of the other (i.e., the two strings are anagrams of each other)

static boolean areAnagrams(String s1, String s2) {
  if (null == s1 && null == s2) {
    return true;
  }
  else if (null == s1 ^ null == s2) {
    return false;
  }
  // Both strings are non-null and identical length
  else if (s1.length() == s2.length()) {
    // char are two-byte primitives in Java
    int numChars = Math.pow(2, 16);

    int[] s1CharCount = new int[numChars];
    int[] s2CharCount = new int[numChars];

    countChars(s1, s1CharCount);
    countChars(s2, s2CharCount);

    for (int i = 0; i < numChars; i++) {
      if (s1CharCount[i] != s2CharCount[i]) {
        return false;
      }
    }
    return true;
  }
  return false;
}

static void countChars(String s, int[] charCount) {
  for (int i = 0; i < s.length(); i++) {
    charCount[Character.numericValue(s.charAt(i))]++;    
  }
}