algorithms/algorithms/strings/decode_string.py at master · pgill2/algorithms · GitHub

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# Given an encoded string, return it's decoded string.

# The encoding rule is: k[encoded_string], where the encoded_string

# inside the square brackets is being repeated exactly k times.

# Note that k is guaranteed to be a positive integer.

# You may assume that the input string is always valid; No extra white spaces,

# square brackets are well-formed, etc.

# Furthermore, you may assume that the original data does not contain any

# digits and that digits are only for those repeat numbers, k.

# For example, there won't be input like 3a or 2[4].

# Examples:

# s = "3[a]2[bc]", return "aaabcbc".

# s = "3[a2[c]]", return "accaccacc".

# s = "2[abc]3[cd]ef", return "abcabccdcdcdef".

def decode_string(s):

"""

:type s: str

:rtype: str

"""

stack = []; cur_num = 0; cur_string = ''

for c in s:

if c == '[':

stack.append((cur_string, cur_num))

cur_string = ''

cur_num = 0

elif c == ']':

prev_string, num = stack.pop()

cur_string = prev_string + num * cur_string

elif c.isdigit():

cur_num = cur_num*10 + int(c)

else:

cur_string += c

return cur_string

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