# 393. UTF-8 Validation

#### Medium

***

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:

1. For a **1-byte** character, the first bit is a `0`, followed by its Unicode code.
2. 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:**

<pre><code>Input: data = [197,130,1]
<strong>Output:
</strong> true
<strong>Explanation:
</strong> 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.
</code></pre>

**Example 2:**

<pre><code>Input: data = [235,140,4]
<strong>Output:
</strong> false
<strong>Explanation:
</strong> 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.
</code></pre>

&#x20;

**Constraints:**

* `1 <= data.length <= 2 * 104`
* `0 <= data[i] <= 255`

```python
class Solution:
    def validUtf8(self, data: List[int]) -> bool:
        data = [str(bin(seq)[2:].zfill(8)) for seq in data]
        while data:
            seq = data.pop(0)
            if seq.startswith("0"): continue
            if seq.startswith("110"):
                if not self.rest(data, 1): return False
            elif seq.startswith("1110"):
                if not self.rest(data, 2): return False
            elif seq.startswith("11110"):
                if not self.rest(data, 3): return False
            else: return False
        return True
        
    def rest(self, data, i):
        if len(data) < i: return False
        for _ in range(i):
            if not data.pop(0).startswith("10"): return False
        return True
```