16R1A-A-lastword.py

import sys
sys.setrecursionlimit(10000)

files = ['A-small-practice.in', 'A-large-practice.in']

def last_word(S, lastw):
    if S == '':
        return lastw
    else:
        return last_word(S[1:], S[0] + lastw if S[0] >= lastw[0] else lastw + S[0])

def solve(fn):
    sol = ''
    with open(fn) as f:
        next(f)

        for case, line in enumerate(f, 1):
            S = line.strip()
            curr = last_word(S[1:], S[0])
            sol += 'Case #{}: {}\n'.format(case, curr)

    with open(fn + '.sol', 'wt') as f:
        f.write(sol)
        print(sol)

for fn in files:
    solve(fn)