String hash function #1

• This hash function adds up the integer values of the chars in the string (then need to take the result mod the size of the table):
  

int hash(std::string const & key) {

	int hashVal = 0, len = key.length();

	for(int i=0; i<len; i++) {

		hashVal += key[i];	}

	return hashVal;

}

• This function is simple to compute, but it often doesn’t work very well in practice:
  
• Suppose the keys are strings of 8 ASCII capital letters and spaces
  
• There are 27 8 possible keys; however, ASCII codes for these characters are in the range 65-95, and so the sums of 8 char values will be in the range 520 - 760
  
• In a large table (M>1000), only a small fraction of the slots would ever be mapped to by this hash function! For a small table (M<100), it may be okay