even.py

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from pyscipopt import Model
 
verbose = False
sdic = {0: "even", 1: "odd"}
 
 
def parity(number):
    try:
        assert number == int(round(number))
        m = Model()
        m.hideOutput()
 
        
        x = m.addVar("x", vtype="I", lb=None, ub=None)  # ub=None is default
        n = m.addVar("n", vtype="I", lb=None)
        s = m.addVar("s", vtype="B")
 
        
        m.addCons(x == number)
 
        m.addCons(s == x - 2 * n)
        m.setObjective(s)
        m.optimize()
 
        assert m.getStatus() == "optimal"
        if verbose:
            for v in m.getVars():
                print("%s %d" % (v, m.getVal(v)))
            print("%d%%2 == %d?" % (m.getVal(x), m.getVal(s)))
            print(m.getVal(s) == m.getVal(x) % 2)
 
        xval = m.getVal(x)
        sval = m.getVal(s)
        sstr = sdic[sval]
        print("%d is %s" % (xval, sstr))
    except (AssertionError, TypeError):
        print("%s is neither even nor odd!" % number.__repr__())
 
 
if __name__ == "__main__":
    import sys
    from ast import literal_eval as leval
 
    example_values = [0, 1, 1.5, "hallo welt", 20, 25, -101, -15., -10, -int(2 ** 31), int(2 ** 31 - 1),
                      int(2 ** 63) - 1]
    try:
        try:
            n = leval(sys.argv[1])
        except ValueError:
            n = sys.argv[1]
        parity(n)
    except IndexError:
        for n in example_values:
            parity(n)