  Flip-sort is a natural sorting procedure which raises fascinating
combinatorial questions. It finds its roots in the seminal work of Knuth on
stack-based sorting algorithms and leads to many links with permutation
patterns. We present several structural, enumerative, and algorithmic results
on permutations that need few (resp. many) iterations of this procedure to be
sorted. In particular, we give the shape of the permutations after one
iteration, and characterize several families of permutations related to the
best and worst cases of flip-sort. En passant, we also give some links between
pop-stack sorting, automata, and lattice paths, and introduce several tactics
of bijective proofs which have their own interest.
