394 decode string

394. Decode String

题目:

https://leetcode.com/problems/decode-string/

难度:

Medium

思路:

感觉像用栈做运算。

s = "3[a2[c]]"

⬇️

s = 3 *( a + 2 * ( c ) )

遇到非右括号全部入栈，碰到右括号出栈直到左括号，这个就算运算符2 → op2 然后检查，直到stack空掉或者碰到下一个非数字，这个就算运算符1 → op1

算出op1 和 op2 之后把这个res继续入栈。然后接着处理

代码不是很优美

class Solution(object):
    def decodeString(self, s):
        """
        :type s: str
        :rtype: str
        """

        s = list(s)
        stack = []

        while s:
            char = s.pop(0)
            if char != ']':
                stack.append(char)
            else:
                op1, op2 = '',''
                popChar = stack.pop()
                while popChar != '[':
                    op2 = popChar + op2
                    popChar = stack.pop()

                while stack and stack[-1] in ['0','1','2','3','4','5','6','7','8','9']:
                    popChar = stack.pop()
                    op1 = popChar + op1

                res = int(op1) * op2

                for char in res:
                    stack.append(char)

        return ''.join(stack)

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