[LeetCode]题解（python）：093 Restore IP Addresses

题目来源

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https://leetcode.com/problems/restore-ip-addresses/

Given a string containing only digits, restore it by returning all possible valid IP address combinations.

For example:
Given "25525511135",

return ["255.255.11.135", "255.255.111.35"]. (Order does not matter)

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题意分析

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Input:一串数字

Output:可能的ip

Conditions:符合0~255

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题目思路

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用dfs，要注意考虑0.0.0.0的情况，不考虑00.00.00.00这样多个0的

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AC代码（Python）

class Solution(object):
    def restoreIpAddresses(self, s):
        """
        :type s: str
        :rtype: List[str]
        """
        def dfs(s, sub, ips, ip):
            if sub == 4:
                if s == "":
                    ips.append(ip[1:])
                return
            for i in range(1,4):
                if i <= len(s):
                    if int(s[:i]) <= 255:
                        dfs(s[i:], sub + 1, ips, ip+"."+s[:i])
                    if s[0] == "0":
                        break
        ips = []
        dfs(s, 0, ips, "")
        return ips