【LeetCode】【String】defanging an IP address

【题目】

给定有效的（IPv4）IP地址，请返回该IP地址的脱机版本。新的IP地址将替换每个句点“.” 与“ [.]”。

Example 1:

Input: address = "1.1.1.1"
Output: "1[.]1[.]1[.]1"

Example 2:

Input: address = "255.100.50.0"
Output: "255[.]100[.]50[.]0"

 

Constraints:

• The given address is a valid IPv4 address.

【解法一】

class Solution:
    def defangIPaddr(self, address: str) -> str:
        new = ""
        for i in address:
            if i == ".":
                new = new + '[.]'
            else:
                new = new + i
        return new

Runtime: 28 ms, faster than 73.31% of Python3 online submissions for Defanging an IP Address.

Memory Usage: 13.7 MB, less than 80.59% of Python3 online submissions for Defanging an IP Address.

【解法】

将"."替换成“[.]”

class Solution:
    def defangIPaddr(self, address: str) -> str:
        ip = address.split(".")
        new = [0]*(len(ip)-1)
        for i in range(0,len(ip)-1):
            new[i] = ip[i]+"[.]"
        new.append(ip[-1])
        return "".join(new)

Runtime: 28 ms, faster than 73.31% of Python3 online submissions for Defanging an IP Address.

Memory Usage: 14 MB, less than 5.10% of Python3 online submissions for Defanging an IP Address.

【解法】

简洁，一句话概括上面的两种解法。

    def defangIPaddr(self, address: str) -> str:
        return address.replace('.', '[.]')
    def defangIPaddr(self, address: str) -> str:
        return '[.]'.join(address.split('.'))
    def defangIPaddr(self, address: str) -> str:
        return re.sub('\.', '[.]', address) #快
    def defangIPaddr(self, address: str) -> str:
        return ''.join('[.]' if c == '.' else c for c in address) #快，且内存占用少

Runtime: 32 ms, faster than 45.10% of Python3 online submissions for Defanging an IP Address.

Memory Usage: 13.8 MB, less than 50.10% of Python3 online submissions for Defanging an IP Address.

 

Runtime: 32 ms, faster than 45.10% of Python3 online submissions for Defanging an IP Address.

Memory Usage: 13.8 MB, less than 43.74% of Python3 online submissions for Defanging an IP Address.

 

Runtime: 24 ms, faster than 91.51% of Python3 online submissions for Defanging an IP Address.

Memory Usage: 13.8 MB, less than 55.07% of Python3 online submissions for Defanging an IP Address.

 

Runtime: 24 ms, faster than 91.51% of Python3 online submissions for Defanging an IP Address.

Memory Usage: 13.7 MB, less than 84.40% of Python3 online submissions for Defanging an IP Address.

 

【Python 函数】replace()方法

Python replace() 方法把字符串中的 old（旧字符串） 替换成 new(新字符串)，如果指定第三个参数max，则替换不超过 max 次。

 

replace()方法语法：str.replace(old, new[, max])

关于 string 的 replace 方法，需要注意 replace 不会改变原 string 的内容。

实例：

temp_str = 'this is a test'
print(temp_str.replace('is','IS')
print(temp_str)

结果为：

thIS IS a test
this is a test