原文地址:https://www.cnblogs.com/strengthen/p/10299741.html
A character in UTF8 can be from 1 to 4 bytes long, subjected to the following rules:
- For 1-byte character, the first bit is a 0, followed by its unicode code.
- For n-bytes character, the first n-bits are all one's, the n+1 bit is 0, followed by n-1 bytes with most significant 2 bits being 10.
This is how the UTF-8 encoding would work:
Char. number range | UTF-8 octet sequence
(hexadecimal) | (binary)
--------------------+---------------------------------------------
0000 0000-0000 007F | 0xxxxxxx
0000 0080-0000 07FF | 110xxxxx 10xxxxxx
0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
Given an array of integers representing the data, return whether it is a valid utf-8 encoding.
Note:
The input is an array of integers. Only the least significant 8 bits of each integer is used to store the data. This means each integer represents only 1 byte of data.
Example 1:
data = [197, 130, 1], which represents the octet sequence: 11000101 10000010 00000001. Return true. It is a valid utf-8 encoding for a 2-bytes character followed by a 1-byte character.
Example 2:
data = [235, 140, 4], which represented the octet sequence: 11101011 10001100 00000100. Return false. The first 3 bits are all one's and the 4th bit is 0 means it is a 3-bytes character. The next byte is a continuation byte which starts with 10 and that's correct. But the second continuation byte does not start with 10, so it is invalid.
UTF-8 中的一个字符可能的长度为 1 到 4 字节,遵循以下的规则:
- 对于 1 字节的字符,字节的第一位设为0,后面7位为这个符号的unicode码。
- 对于 n 字节的字符 (n > 1),第一个字节的前 n 位都设为1,第 n+1 位设为0,后面字节的前两位一律设为10。剩下的没有提及的二进制位,全部为这个符号的unicode码。
这是 UTF-8 编码的工作方式:
Char. number range | UTF-8 octet sequence
(hexadecimal) | (binary)
--------------------+---------------------------------------------
0000 0000-0000 007F | 0xxxxxxx
0000 0080-0000 07FF | 110xxxxx 10xxxxxx
0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
给定一个表示数据的整数数组,返回它是否为有效的 utf-8 编码。
注意:
输入是整数数组。只有每个整数的最低 8 个有效位用来存储数据。这意味着每个整数只表示 1 字节的数据。
示例 1:
data = [197, 130, 1], 表示 8 位的序列: 11000101 10000010 00000001. 返回 true 。 这是有效的 utf-8 编码,为一个2字节字符,跟着一个1字节字符。
示例 2:
data = [235, 140, 4], 表示 8 位的序列: 11101011 10001100 00000100. 返回 false 。 前 3 位都是 1 ,第 4 位为 0 表示它是一个3字节字符。 下一个字节是开头为 10 的延续字节,这是正确的。 但第二个延续字节不以 10 开头,所以是不符合规则的。
104ms
1 class Solution { 2 func validUtf8(_ data: [Int]) -> Bool { 3 var cnt:Int = 0 4 for d in data 5 { 6 if cnt == 0 7 { 8 if (d >> 5) == 0b110 {cnt = 1} 9 else if (d >> 4) == 0b1110 {cnt = 2} 10 else if (d >> 3) == 0b11110 {cnt = 3} 11 else if d >> 7 == 1 {return false} 12 //else if d>>7 == 0b1 { return false } 13 } 14 else 15 { 16 if (d >> 6) != 0b10 {return false} 17 cnt -= 1 18 } 19 } 20 return cnt == 0 21 } 22 }