leetcode 393. UTF-8 Validation（UTF-8 编码验证）

最新推荐文章于 2025-04-03 09:38:08 发布

原创

最新推荐文章于 2025-04-03 09:38:08 发布 · 284 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#leetcode #算法

该博客探讨了如何验证一个整数数组是否代表有效的UTF-8编码。UTF-8编码规则包括1至4字节字符的定义，博客通过示例解释了编码的工作原理，并提供了两种不同的Java代码实现来检查输入数据的合法性。代码通过位移操作或与运算来判断每个字节是否符合UTF-8编码标准。

Given an integer array data representing the data, return whether it is a valid UTF-8 encoding (i.e. it translates to a sequence of valid UTF-8 encoded characters).

A character in UTF8 can be from 1 to 4 bytes long, subjected to the following rules:

For a 1-byte character, the first bit is a 0, followed by its Unicode code.
For an n-bytes character, the first n bits are all one’s, the n + 1 bit is 0, followed by n - 1 bytes with the most significant 2 bits being 10.
This is how the UTF-8 encoding would work:

     Number of Bytes   |        UTF-8 Octet Sequence
                       |              (binary)
   --------------------+-----------------------------------------
            1          |   0xxxxxxx
            2          |   110xxxxx 10xxxxxx
            3          |   1110xxxx 10xxxxxx 10xxxxxx
            4          |   11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

x denotes a bit in the binary form of a byte that may be either 0 or 1.

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:

Input: data = [197,130,1]
Output: true
Explanation: data represents the octet sequence: 11000101 10000010 00000001.
It is a valid utf-8 encoding for a 2-bytes character followed by a 1-byte character.
Example 2:

Input: data = [235,140,4]
Output: false
Explanation: data represented the octet sequence: 11101011 10001100 00000100.
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.

看着很绕，简单解释下，
UFT-8是1～4byte长的，不能超过4byte.
4个byte可能出现的4种情况都在表里，不符合的就是false。
那你会说1 <= data.length <= 20000，data的长度可能到20000啊，怎么可能只有4 byte。
1～4 byte代表一个字符，后面的就是另一个字符，1～4 byte为一组。