justinbutler700 / utf-8-validation-leetcode-medium

1ms beats 100% Java solution to UTF-8 Validation

UTF-8-Validation-Leetcode-Medium

1ms beats 100% Java solution to UTF-8 Validation

Link to Question: https://leetcode.com/problems/utf-8-validation/

Instructions: 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:

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 2:

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.

Constraints:

1 <= data.length <= 2 * 10^4 0 <= data[i] <= 255