输入:s = "3[a]2[bc]" 输出:"aaabcbc"
class Solution(object):
def decodeString(self, s):
"""
:type s: str
:rtype: str
"""
stack=[]
res = ''
multi = 0
for c in s:
if '0' <= c <= '9':
multi = 10*multi+int(c)
elif c == '[':
stack.append((res, multi))
res = ''
multi = 0
elif c == ']':
last_res, last_multi = stack.pop()
res = last_res+res*last_multi
else:
res += c
return res