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First solution in Clear category for Count Inversions by makoto_yamagata
def count_inversion(sequence, inversion=0):
if not sequence: return inversion
head, *tail = sequence
return count_inversion(tail, inversion+sum(head > x for x in tail))
if __name__ == '__main__':
#These "asserts" using only for self-checking and not necessary for auto-testing
assert count_inversion((1, 2, 5, 3, 4, 7, 6)) == 3, "Example"
assert count_inversion((0, 1, 2, 3)) == 0, "Sorted"
assert count_inversion((99, -99)) == 1, "Two numbers"
assert count_inversion((5, 3, 2, 1, 0)) == 10, "Reversed"
July 12, 2015
