Source code for tryalgo.three_partition

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""\
subsetsum
jill-jênn vie et christoph dürr - 2015-2019
"""


# snip{
[docs]def three_partition(x): """partition a set of integers in 3 parts of same total value :param x: table of non negative values :returns: triplet of the integers encoding the sets, or None otherwise :complexity: :math:`O(2^{2n})` """ f = [0] * (1 << len(x)) for i, _ in enumerate(x): for S in range(1 << i): f[S | (1 << i)] = f[S] + x[i] for A in range(1 << len(x)): for B in range(1 << len(x)): if A & B == 0 and f[A] == f[B] and 3 * f[A] == f[-1]: return (A, B, ((1 << len(x)) - 1) ^ A ^ B) return None
# snip}