hasSameCharacters with minor optimization for short strings

hasSameCharacters.cpp

// Expected behavior:
// 'abc', 'cba' => true
// 'abca', 'cba' => true
// 'cba', 'abca' => true
// '', '' => true
// 'abcd', 'abc' => false
// 'abc', 'abcd' => false

bool hasSameCharacters(char* c1, char* c2)
{
  // returning false was how we decided to handle invalid input
  if(c1==NULL || c2==NULL) {
    return false;
  }

  // char has 256 values, so we track characters found in these arrays 
  bool bc1[256] = {0};
  bool bc2[256] = {0};

  /*
  * Short String Optimization: rather than compare bc1 and bc2 at end, we do 2 things:
  * (SSO-1) Return as soon as we find char in c2 that was not in c1
  * (SSO-2) Count and compare unique characters in each string at the end
  *
  * Idea: If c1 and c2 have the same number of unique characters
  *       and every char in c2 is also in c1, 
  *       then we can conclude that every char in c1 is also in c2.
  */
  int uniquec1 = 0;
  int uniquec2 = 0;


  for(int i=0; c1[i] != '\0'; ++i) {
    int offset = c1[i];

    // Found unique char in c1
    if( bc1[offset] == false ) {
      uniquec1++;
      bc1[offset] = true;
    }
  }

  for(int i=0; c2[i] != '\0'; ++i) {
    int offset = c2[i];

    // (SSO-1): No point in continuing if char was not in c1
    if( bc1[offset] == false ) {
      return false;
    }

    // Found unique char in c2
    if( bc2[offset] == false ) {
      uniquec2++;
      bc2[offset] = true;
    } 
  }

  // (SSO-2): Compare unique character counts
  return (uniquec1 == uniquec2);
}