Head-tail is a classic recursion algorithm.
To reverse a string we place the head behind tail.
A permutation is a specific order of a set.
To find permutations we select one element as the head.
What is the head-tail technique?
How do we reverse a string?
What is a permutation of a set {A,B,C}?
How can we find the permutations of a set?
2010 - 2023 
Php
Algorithms