Solving lecture 45 challenge in O(n).

Lecture 45 challenge.cpp

bool IsWordIsogram(std::string Word)
{
  // This create an array of size 26 initialized with 0 in every index.
  int arr[26] = {};
  
  // For each letter in the Word
  for(int i = 0; i < Word.length(); i++)
  {
    // this subtract the value of character 'a' from the character that we are looking for like 'a'-'b' = 1;
    int index = 'a'-Word[i];
    
    // Go to that index and mark that we have a letter of that kind.
    arr[index]++;
    
    // Check if we have more than one letter of that kind.
    if(arr[index] >= 2)
      return false; // We have more than two letters of same kind, so it's not a isogram.
  }
  return true; // This word is a isogram.
}