# [393. UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/)



## 题目

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

1. For 1-byte character, the first bit is a 0, followed by its unicode code.
2. 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.

## 题目大意

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：

```c
   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。


## 解题思路

- 这一题看似很复杂，其实严格按照 UTF8 定义来模拟就可以了。