"""Leetcode 393. UTF-8 Validation
Medium

URL: https://leetcode.com/problems/utf-8-validation/

A character in UTF8 can be from 1 to 4 bytes long, subjected to the following rules:
- For 1-byte character, the first bit is a 0, followed by its unicode code.
- 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.
"""

class Solution(object):
    def validUtf8(self, data):
        """
        :type data: List[int]
        :rtype: bool
        """
        pass


def main():
    pass


if __name__ == '__main__':
    main()

"""Leetcode 393. UTF-8 Validation
Medium

URL: https://leetcode.com/problems/utf-8-validation/

A character in UTF8 can be from 1 to 4 bytes long, subjected to the following rules:
- For 1-byte character, the first bit is a 0, followed by its unicode code.
- 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.
"""

class SolutionBitShiftNumRhsBytes(object):
    def validUtf8(self, data):
        """
        :type data: List[int]
        :rtype: bool

        Time complexity: O(n), where n is length of data.
        Space complexity: O(1).
        """
        n_rhs_bytes = 0

        for d in data:
            # In 1st iteration check number of RHS bytes.
            if n_rhs_bytes == 0:
                if d >> 3 == 0b11110:
                    n_rhs_bytes = 3
                elif d >> 4 == 0b1110:
                    n_rhs_bytes = 2
                elif d >> 5 == 0b110:
                    n_rhs_bytes = 1
                elif d >> 7 != 0:
                    return False
            else:
                # For RHS bytes, check if marker matches pattern.
                if n_rhs_bytes < 0 or d >> 6 != 0b10:
                    return False
                n_rhs_bytes -= 1

        return n_rhs_bytes == 0


def main():
    # Output: True
    data = [197, 130, 1]
    print SolutionBitShiftNumRhsBytes().validUtf8(data)

    # Output: False
    data = [235, 140, 4]
    print SolutionBitShiftNumRhsBytes().validUtf8(data)


if __name__ == '__main__':
    main()

Complete bit oper num rhs bytes