UTF-8 Validation — LeetCode 393 Python Solution

The problem

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).

Example

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

Python solution

class Solution:
    def validUtf8(self, data: List[int]) -> bool:
        cnt = 0
        for v in data:
            if cnt > 0:
                if v >> 6 != 0b10:
                    return False
                cnt -= 1
            elif v >> 7 == 0:
                cnt = 0
            elif v >> 5 == 0b110:
                cnt = 1
            elif v >> 4 == 0b1110:
                cnt = 2
            elif v >> 3 == 0b11110:
                cnt = 3
            else:
                return False
        return cnt == 0

Complexity

Pattern: Bit Manipulation

Use XOR, masks and the low-bit trick to replace whole data structures with an integer. LeetCode 393. UTF-8 Validation is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Bit Manipulation.

The bit manipulation guide has the Python template for the pattern and the 194 LeetCode problems that use it.

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