Decode String
Created: March 25, 2020 by [lek-tin]
Last updated: March 25, 2020
Given an encoded string, return its 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".
Solution
class Solution:
def decodeString(self, s: str) -> str:
N = len(s)
countStack, strStack = [], []
tempCount = ""
strStack.append("")
if N == 0:
return ""
for c in s:
if c.isdigit():
tempCount += c
elif c == "[":
countStack.append( int(tempCount) )
tempCount = ""
strStack.append("")
elif c == "]":
tempStr = strStack.pop()
count = countStack.pop()
strStack.append( strStack.pop() + tempStr * count )
else:
# append c to tempStr then update stack with new tempStr
strStack.append(strStack.pop() + c)
return strStack.pop()