leetcode刷题笔记-stack

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/Sengo_GWU/article/details/81845004

394. Decode String

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".

class Solution(object):
    def decodeString(self, s):
        """
        :type s: str
        :rtype: str
        """
        stack = [["", 1]]
        num = ""
        for ch in s:
            if ch.isdigit():
                num += ch
            elif ch == '[':
                stack.append(['', int(num)])
                num = ''
            elif ch == ']':
                stri, k = stack.pop()
                stack[-1][0] += stri*k
            else:
                stack[-1][0] += ch
        return stack[0][0]