Codejam 2018 Qualification Round Problem 1a,b

universe.py

def reader():
    """ read the input from stdin """
    N = int(input())
    tcs = []
    for i in range(N):
        (l, instructions) = input().split(" ")
        tcs.append((int(l), instructions))
    return tcs

def damage(instructions):
    """ Calculates the damage the spaceship will do given an instruction string """
    dmg = 0
    current = 1
    if instructions is None:
        return 0
    for i in instructions:
        if i == 'C':
            current *=2
        else:
            dmg += current
    return dmg

def greedy_swap(instructions):
    """ Replace instructions with new instructions, less harmful ones """
    rev = instructions[::-1]
    if "SC" in rev:
        return rev.replace("SC", "CS", 1)[::-1]
    else:
        # Return None to signify you can't do anything more
        return None

def solver(D, instructions):
    """Solver"""
    i = 0
    while instructions:
        cost = damage(instructions)
        if cost <= D:
            # Either you managed to mitigate the damage
            return i
        instructions = greedy_swap(instructions)
        i += 1
    # Or you can't
    return "IMPOSSIBLE"

import sys
for i, (x, y)  in enumerate(reader()):
    print("Case #{}: {}".format(i, solver(x,y)))
    sys.stdout.flush()

Codejam 2018 Qualification Round solution for Problem 1 (small + big)