UTF-8 Validation

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Description

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:

Number of Bytes | UTF-8 Octet Sequence

| (binary)

--------------------+-----------------------------------------

1 | 0xxxxxxx

2 | 110xxxxx 10xxxxxx

3 | 1110xxxx 10xxxxxx 10xxxxxx

4 | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

Example 2:

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 3:

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.

Solution