Heidi was trying to solve the anagram TORYS by rearranging every letter one at a time until she was able to identify the correct word: STORY. She could have attempted to solve the anagram more quickly by pairing common letters, like ST, but she did not do so. Her approach to solving the anagram involved

Paring up common letters would involve using a heuristic. Heidi used an algorithm, a strict rule, instead.