def _reversal_sort_log(d, p):
'''Print a shortest path log from the identity permutation to the permutation p.'''
d_rev, start, stop = d[p]
print d_rev
print start + 1, stop
for _ in xrange(d_rev - 1):
p = rr.reverse(p, (start, stop))
_, start, stop = d[p]
print start + 1, stop
def all_reverses_with_moves(p):
'''A generator of all possible reverses of a permutation p.'''
n = len(p)
return ((rr.reverse(p, (j, k)), (j, k)) for j in xrange(n - 1) for k in xrange(j + 2, n + 1))
