leetcode468. Validate IP Address
- 2019 年 10 月 11 日
- 筆記
題目要求
Write a function to check whether an input string is a valid IPv4 address or IPv6 address or neither. IPv4 addresses are canonically represented in dot-decimal notation, which consists of four decimal numbers, each ranging from 0 to 255, separated by dots ("."), e.g.,172.16.254.1; Besides, leading zeros in the IPv4 is invalid. For example, the address 172.16.254.01 is invalid. IPv6 addresses are represented as eight groups of four hexadecimal digits, each group representing 16 bits. The groups are separated by colons (":"). For example, the address 2001:0db8:85a3:0000:0000:8a2e:0370:7334 is a valid one. Also, we could omit some leading zeros among four hexadecimal digits and some low-case characters in the address to upper-case ones, so 2001:db8:85a3:0:0:8A2E:0370:7334 is also a valid IPv6 address(Omit leading zeros and using upper cases). However, we don't replace a consecutive group of zero value with a single empty group using two consecutive colons (::) to pursue simplicity. For example, 2001:0db8:85a3::8A2E:0370:7334 is an invalid IPv6 address. Besides, extra leading zeros in the IPv6 is also invalid. For example, the address 02001:0db8:85a3:0000:0000:8a2e:0370:7334 is invalid. Note: You may assume there is no extra space or special characters in the input string. Example 1: Input: "172.16.254.1" Output: "IPv4" Explanation: This is a valid IPv4 address, return "IPv4". Example 2: Input: "2001:0db8:85a3:0:0:8A2E:0370:7334" Output: "IPv6" Explanation: This is a valid IPv6 address, return "IPv6". Example 3: Input: "256.256.256.256" Output: "Neither" Explanation: This is neither a IPv4 address nor a IPv6 address.
校驗該字元串是IPV4地址還是IPV6地址還是二者都不是。 IPV4地址通過小數點分割為4個部分，每個部分都是0～255之間的正整數，且不能包含開頭的0，如013 IPV6地址通過冒號分割為8個部分，允許以0作為開頭，但是每個部分不能用空代替0。
思路和程式碼
其實這題考驗的是測試思維，即如何能夠把所有的邊界情況考慮清楚。這裡我簡單列舉一下幾個邊界場景
- IPV4地址中小數點個數超過3個
- IPV4地址中小數點分割開來的每個部分中包含非整數值
- IPV4地址中小數點分割開來的每個部分數值不再0～255之間
- IPV6地址中冒號個數超過7個
- IPV6地址中分割開來的每個部分包含空值
- IPV6地址中分割出來的每個部分長度不是1～4
- IPV6地址中分割出來的每個部分包含非16進位數中包含的內容
程式碼如下：
private static final String IPV4 = "IPv4"; private static final String IPV6 = "IPv6"; private static final String NEITHER = "Neither"; public String validIPAddress(String IP) { if (IP==null ||IP.isEmpty()) {return NEITHER;} if (IP.contains(".")) { return checkIPv4(IP); }else if (IP.contains(":")) { return checkIPv6(IP); }else { return NEITHER; } } private String checkIPv4(String IP) { if (IP.startsWith(".") || IP.endsWith(".")) {return NEITHER;} String[] addressParts = IP.split("\."); if (addressParts.length != 4) { return NEITHER; } for (String addressPart :addressParts) { if (addressPart.length() <= 0 || addressPart.length() > 3 || addressPart.startsWith("0") && addressPart.length() > 1 ) { return NEITHER; } int value = 0; for (char c : addressPart.toCharArray()) { if (c < '0' || c > '9') { return NEITHER; } value = value * 10 + (c - '0'); } if (value < 0 || value > 255) { return NEITHER; } } return IPV4; } private String checkIPv6(String IP) { if (IP.startsWith(":") || IP.endsWith(":")) {return NEITHER;} String[] addressParts = IP.split(":"); if (addressParts.length != 8) { return NEITHER; } for (String addressPart : addressParts) { if (addressPart.length() <= 0 || addressPart.length() > 4) { return NEITHER; } for (char c : addressPart.toCharArray()) { char lowerChar = Character.toLowerCase(c); if (!((lowerChar >= '0' && lowerChar <= '9') || (lowerChar >= 'a' && lowerChar <= 'f'))) { return NEITHER; } } } return IPV6; }
