DecodeString.py

#
# https://leetcode.com/problems/decode-string/description/
#
class Solution(object):
    def decodeString(self, s):
        """
        :type s: str
        :rtype: str
        """
        nums = [] # 3
        letters = [] #
        result = None
        prev = ''
        for i in s:
            if i.isdigit():
                val = nums.pop() if prev.isdigit() and len(nums) else ''
                nums.append(val + i)
                # print 'num: ' + i
            elif i.isalpha():
                val = letters.pop() if prev.isalpha() and len(letters) else ''
                letters.append(val + i)
            elif i == ']':
                print nums
                print letters
                if result == None:
                    result = int(nums.pop()) * letters.pop()
                else:
                    result   
                # result += int(nums.pop()) * letters.pop() 
                print result
            prev = i

        return result

str = Solution();
print str.decodeString('3[a2[c]]')