题目：
复原IP地址：给定一个只包含数字的字符串，复原它并返回所有可能的 IP 地址格式。 有效的 IP 地址正好由四个整数（每个整数位于 0 到 255 之间组成），整数之间用 '.' 分隔。
思路：
思路较简单。
程序：
class Solution:
def restoreIpAddresses(self, s: str) -> List[str]:
if not s:
return []
length = len(s)
if length < 4:
return []
result = []
for index1 in range(1, 4):
section1 = s[0: index1]
if self.judgeIfValid(section1):
for index2 in range(index1 + 1, index1 + 4):
section2 = s[index1: index2]
if self.judgeIfValid(section2):
for index3 in range(index2 + 1, index2 + 4):
section3 = s[index2: index3]
if self.judgeIfValid(section3):
section4 = s[index3:]
if self.judgeIfValid(section4):
result.append("%s.%s.%s.%s" %(section1, section2, section3, section4))
ip = result
return ip
def judgeIfValid(self, section):
if section and section[0] == "0" and len(section) > 1:
return False
if section and int(section) == 0 and len(section) > 1:
return False
if section and len(section) > 3:
return False
if section and int(section) >= 0 and int(section) <= 255:
return True
else:
return False