hasSameCharacters simple O(n) solution

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};

  for(int i=0; c1[i] != '\0'; ++i) {
    int offset = c1[i];
    bc1[offset] = true;
  }

  for(int i=0; c2[i] != '\0'; ++i) {
    int offset = c2[i];
    bc2[offset] = true;
  }

  for(int i=0; i<256; ++i) {
    if(bc1[i] != bc2[i]) {
      return false;
    }
  }
 
 return true;
}