Prefix reversal
= Prefix reversal
Reverse the first $k$ entries of a <sequence> and leave its suffix unchanged. On a <permutation>, this is a bijection on positions and is its own inverse: performing the same reversal twice restores the state. The nontrivial moves have $2\leq k\leq n$. With unit-cost moves, the resulting state graph supports a <breadth-first search> for a minimum-move solution.