In [3]:

def cycleToChromosome(nodes):
    """ Input: A sequence Nodes of integers between 1 and 2n.
        Output: The chromosome Chromosome containing n synteny blocks resulting from applying
        CycleToChromosome to Nodes."""
    chromosome = []
    for j in range(len(nodes)/2):
        if nodes[2*j] < nodes[2*j + 1]:
            chromosome.append(nodes[2*j + 1]/2)
        else:
            chromosome.append(-nodes[2*j]/2)
    return chromosome    

In [4]:

nodes = [1, 2, 4, 3, 6, 5, 7, 8]
cycleToChromosome(nodes)

Out[4]:

[1, -2, -3, 4]

In [13]:

f = open('input/rosalind_ba6g.txt')
nodes = map(int, f.read().strip().lstrip('(').rstrip(')').split())
ans = cycleToChromosome(nodes)
output = '('+' '.join([['', '+'][value > 0] + str(value) for value in ans])+')'
print(output)

(-1 +2 -3 +4 -5 -6 +7 +8 +9 +10 -11 +12 -13 +14 +15 -16 -17 +18 -19 +20 -21 -22 -23 -24 +25 -26 -27 +28 -29 +30 +31 +32 -33 -34 +35 -36 -37 -38 -39 -40 -41 -42 +43 -44 -45 +46 -47 +48 -49 +50 -51 +52 +53 -54 +55 +56 -57 -58 +59 +60 +61 +62 -63 -64 -65 -66)

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