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README_EN.md

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468. Validate IP Address

中文文档

Description

Given a string queryIP, return "IPv4" if IP is a valid IPv4 address, "IPv6" if IP is a valid IPv6 address or "Neither" if IP is not a correct IP of any type.

A valid IPv4 address is an IP in the form "x1.x2.x3.x4" where 0 <= xi <= 255 and xi cannot contain leading zeros. For example, "192.168.1.1" and "192.168.1.0" are valid IPv4 addresses while "192.168.01.1", "192.168.1.00", and "192.168@1.1" are invalid IPv4 addresses.

A valid IPv6 address is an IP in the form "x1:x2:x3:x4:x5:x6:x7:x8" where:

  • 1 <= xi.length <= 4
  • xi is a hexadecimal string which may contain digits, lowercase English letter ('a' to 'f') and upper-case English letters ('A' to 'F').
  • Leading zeros are allowed in xi.

For example, "2001:0db8:85a3:0000:0000:8a2e:0370:7334" and "2001:db8:85a3:0:0:8A2E:0370:7334" are valid IPv6 addresses, while "2001:0db8:85a3::8A2E:037j:7334" and "02001:0db8:85a3:0000:0000:8a2e:0370:7334" are invalid IPv6 addresses.

 

Example 1:

Input: queryIP = "172.16.254.1"
Output: "IPv4"
Explanation: This is a valid IPv4 address, return "IPv4".

Example 2:

Input: queryIP = "2001:0db8:85a3:0:0:8A2E:0370:7334"
Output: "IPv6"
Explanation: This is a valid IPv6 address, return "IPv6".

Example 3:

Input: queryIP = "256.256.256.256"
Output: "Neither"
Explanation: This is neither a IPv4 address nor a IPv6 address.

 

Constraints:

  • queryIP consists only of English letters, digits and the characters '.' and ':'.

Solutions

Solution 1: Simulation

We can define two functions isIPv4 and isIPv6 to determine whether a string is a valid IPv4 address and IPv6 address.

The implementation of the function isIPv4 is as follows:

  1. We first check if the string s ends with .. If so, s is not a valid IPv4 address, and we directly return false.
  2. Then we split the string s by . into a string array ss. If the length of ss is not 4, s is not a valid IPv4 address, and we directly return false.
  3. For each string t in the array ss, we check:
    • If the length of t is greater than 1 and the first character of t is 0, t is not a valid IPv4 address, and we directly return false.
    • If t is not a number or t is not in the range of 0 to 255, t is not a valid IPv4 address, and we directly return false.
  4. If none of the above conditions are met, s is a valid IPv4 address, and we return true.

The implementation of the function isIPv6 is as follows:

  1. We first check if the string s ends with :. If so, s is not a valid IPv6 address, and we directly return false.
  2. Then we split the string s by : into a string array ss. If the length of ss is not 8, s is not a valid IPv6 address, and we directly return false.
  3. For each string t in the array ss, we check:
    • If the length of t is less than 1 or greater than 4, t is not a valid IPv6 address, and we directly return false.
    • If the characters in t are not all between 0 and 9 and a and f (case insensitive), t is not a valid IPv6 address, and we directly return false.
  4. If none of the above conditions are met, s is a valid IPv6 address, and we return true.

Finally, we call the isIPv4 and isIPv6 functions to determine if queryIP is a valid IPv4 address or IPv6 address. If it is neither, we return Neither.

The time complexity is O(n), and the space complexity is O(n). Where n is the length of the string queryIP.

Python3

class Solution:
    def validIPAddress(self, queryIP: str) -> str:
        def is_ipv4(s: str) -> bool:
            ss = s.split(".")
            if len(ss) != 4:
                return False
            for t in ss:
                if len(t) > 1 and t[0] == "0":
                    return False
                if not t.isdigit() or not 0 <= int(t) <= 255:
                    return False
            return True

        def is_ipv6(s: str) -> bool:
            ss = s.split(":")
            if len(ss) != 8:
                return False
            for t in ss:
                if not 1 <= len(t) <= 4:
                    return False
                if not all(c in "0123456789abcdefABCDEF" for c in t):
                    return False
            return True

        if is_ipv4(queryIP):
            return "IPv4"
        if is_ipv6(queryIP):
            return "IPv6"
        return "Neither"

Java

class Solution {
    public String validIPAddress(String queryIP) {
        if (isIPv4(queryIP)) {
            return "IPv4";
        }
        if (isIPv6(queryIP)) {
            return "IPv6";
        }
        return "Neither";
    }

    private boolean isIPv4(String s) {
        if (s.endsWith(".")) {
            return false;
        }
        String[] ss = s.split("\\.");
        if (ss.length != 4) {
            return false;
        }
        for (String t : ss) {
            if (t.length() == 0 || t.length() > 1 && t.charAt(0) == '0') {
                return false;
            }
            int x = convert(t);
            if (x < 0 || x > 255) {
                return false;
            }
        }
        return true;
    }

    private boolean isIPv6(String s) {
        if (s.endsWith(":")) {
            return false;
        }
        String[] ss = s.split(":");
        if (ss.length != 8) {
            return false;
        }
        for (String t : ss) {
            if (t.length() < 1 || t.length() > 4) {
                return false;
            }
            for (char c : t.toCharArray()) {
                if (!Character.isDigit(c)
                    && !"0123456789abcdefABCDEF".contains(String.valueOf(c))) {
                    return false;
                }
            }
        }
        return true;
    }

    private int convert(String s) {
        int x = 0;
        for (char c : s.toCharArray()) {
            if (!Character.isDigit(c)) {
                return -1;
            }
            x = x * 10 + (c - '0');
            if (x > 255) {
                return x;
            }
        }
        return x;
    }
}

C++

class Solution {
public:
    string validIPAddress(string queryIP) {
        if (isIPv4(queryIP)) {
            return "IPv4";
        }
        if (isIPv6(queryIP)) {
            return "IPv6";
        }
        return "Neither";
    }

private:
    bool isIPv4(const string& s) {
        if (s.empty() || s.back() == '.') {
            return false;
        }
        vector<string> ss = split(s, '.');
        if (ss.size() != 4) {
            return false;
        }
        for (const string& t : ss) {
            if (t.empty() || (t.size() > 1 && t[0] == '0')) {
                return false;
            }
            int x = convert(t);
            if (x < 0 || x > 255) {
                return false;
            }
        }
        return true;
    }

    bool isIPv6(const string& s) {
        if (s.empty() || s.back() == ':') {
            return false;
        }
        vector<string> ss = split(s, ':');
        if (ss.size() != 8) {
            return false;
        }
        for (const string& t : ss) {
            if (t.size() < 1 || t.size() > 4) {
                return false;
            }
            for (char c : t) {
                if (!isxdigit(c)) {
                    return false;
                }
            }
        }
        return true;
    }

    int convert(const string& s) {
        int x = 0;
        for (char c : s) {
            if (!isdigit(c)) {
                return -1;
            }
            x = x * 10 + (c - '0');
            if (x > 255) {
                return x;
            }
        }
        return x;
    }

    vector<string> split(const string& s, char delimiter) {
        vector<string> tokens;
        string token;
        istringstream iss(s);
        while (getline(iss, token, delimiter)) {
            tokens.push_back(token);
        }
        return tokens;
    }
};

Go

func validIPAddress(queryIP string) string {
	if isIPv4(queryIP) {
		return "IPv4"
	}
	if isIPv6(queryIP) {
		return "IPv6"
	}
	return "Neither"
}

func isIPv4(s string) bool {
	if strings.HasSuffix(s, ".") {
		return false
	}
	ss := strings.Split(s, ".")
	if len(ss) != 4 {
		return false
	}
	for _, t := range ss {
		if len(t) == 0 || (len(t) > 1 && t[0] == '0') {
			return false
		}
		x := convert(t)
		if x < 0 || x > 255 {
			return false
		}
	}
	return true
}

func isIPv6(s string) bool {
	if strings.HasSuffix(s, ":") {
		return false
	}
	ss := strings.Split(s, ":")
	if len(ss) != 8 {
		return false
	}
	for _, t := range ss {
		if len(t) < 1 || len(t) > 4 {
			return false
		}
		for _, c := range t {
			if !unicode.IsDigit(c) && !strings.ContainsRune("0123456789abcdefABCDEF", c) {
				return false
			}
		}
	}
	return true
}

func convert(s string) int {
	x := 0
	for _, c := range s {
		if !unicode.IsDigit(c) {
			return -1
		}
		x = x*10 + int(c-'0')
		if x > 255 {
			return x
		}
	}
	return x
}

TypeScript

function validIPAddress(queryIP: string): string {
    if (isIPv4(queryIP)) {
        return 'IPv4';
    }
    if (isIPv6(queryIP)) {
        return 'IPv6';
    }
    return 'Neither';
}

function isIPv4(s: string): boolean {
    if (s.endsWith('.')) {
        return false;
    }
    const ss = s.split('.');
    if (ss.length !== 4) {
        return false;
    }
    for (const t of ss) {
        if (t.length === 0 || (t.length > 1 && t[0] === '0')) {
            return false;
        }
        const x = convert(t);
        if (x < 0 || x > 255) {
            return false;
        }
    }
    return true;
}

function isIPv6(s: string): boolean {
    if (s.endsWith(':')) {
        return false;
    }
    const ss = s.split(':');
    if (ss.length !== 8) {
        return false;
    }
    for (const t of ss) {
        if (t.length < 1 || t.length > 4) {
            return false;
        }
        for (const c of t) {
            if (!isHexDigit(c)) {
                return false;
            }
        }
    }
    return true;
}

function convert(s: string): number {
    let x = 0;
    for (const c of s) {
        if (!isDigit(c)) {
            return -1;
        }
        x = x * 10 + (c.charCodeAt(0) - '0'.charCodeAt(0));
        if (x > 255) {
            return x;
        }
    }
    return x;
}

function isDigit(c: string): boolean {
    return c >= '0' && c <= '9';
}

function isHexDigit(c: string): boolean {
    return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F');
}

Rust

impl Solution {
    pub fn valid_ip_address(query_ip: String) -> String {
        if Self::is_ipv4(&query_ip) {
            return "IPv4".to_string();
        }
        if Self::is_ipv6(&query_ip) {
            return "IPv6".to_string();
        }
        "Neither".to_string()
    }

    fn is_ipv4(s: &str) -> bool {
        if s.ends_with('.') {
            return false;
        }
        let ss: Vec<&str> = s.split('.').collect();
        if ss.len() != 4 {
            return false;
        }
        for t in ss {
            if t.is_empty() || (t.len() > 1 && t.starts_with('0')) {
                return false;
            }
            match Self::convert(t) {
                Some(x) if x <= 255 => {
                    continue;
                }
                _ => {
                    return false;
                }
            }
        }
        true
    }

    fn is_ipv6(s: &str) -> bool {
        if s.ends_with(':') {
            return false;
        }
        let ss: Vec<&str> = s.split(':').collect();
        if ss.len() != 8 {
            return false;
        }
        for t in ss {
            if t.len() < 1 || t.len() > 4 {
                return false;
            }
            if !t.chars().all(|c| c.is_digit(16)) {
                return false;
            }
        }
        true
    }

    fn convert(s: &str) -> Option<i32> {
        let mut x = 0;
        for c in s.chars() {
            if !c.is_digit(10) {
                return None;
            }
            x = x * 10 + (c.to_digit(10).unwrap() as i32);
            if x > 255 {
                return Some(x);
            }
        }
        Some(x)
    }
}