LeetCode - UTF-8 Validation

Question Definition

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.

Java Solution

public boolean validUtf8(int[] data) {
    for(int i = 0; i < data.length; i++){
        if(data[i] <= 127){
            continue;
        }
        if(data[i] >= 192 && data[i] <= 223){
            if(i >= data.length - 1 || data[i + 1] < 128 || data[i + 1] > 191)
                return false;
            i++;
            continue;
        }
        if(data[i] >= 224 && data[i] <= 239){
            if(i >= data.length - 2 || data[i + 1] < 128 || data[i + 1] > 191 || data[i + 2] < 128 || data[i + 2] > 191)
                return false;
            i += 2;
            continue;
        }
        if(data[i] >= 240 && data[i] <= 247){
            if(i >= data.length - 3 || data[i + 1] < 128 || data[i + 1] > 191 || data[i + 2] < 128 || data[i + 2] > 191
               || data[i + 3] < 128 || data[i + 3] > 191)
                return false;
            i += 3;
            continue;
        }
        return false;
    }
    return true;
}