tvl-depot/data_structures_and_algorithms/merge-sort.py

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# merge :: [a] -> [a] -> [a]
# merge([], []): []
# merge(xs, []): xs
# merge([], ys): ys
# merge(xs@[x|xs'], ys@[y|ys'])
# when y =< x: cons(y, merge(xs, ys'))
# when x < y: cons(x, merge(xs', ys))
def merge(xs, ys):
if xs == [] and ys == []:
return []
elif ys == []:
return xs
elif xs == []:
return ys
else:
x = xs[0]
y = ys[0]
if y <= x:
return [y] + merge(xs, ys[1:])
else:
return [x] + merge(xs[1:], ys)
print(merge([3, 4, 6, 10, 11, 15],
[1, 5, 8, 12, 14, 19]))