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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0301_0400.s0393_utf_8_validation;

// #Medium #Array #Bit_Manipulation #2022_07_13_Time_1_ms_(100.00%)_Space_43_MB_(87.62%)

/**
 * 393 - UTF-8 Validation\.
 *
 * Medium
 *
 * Given an integer array `data` representing the data, return whether it is a valid **UTF-8** encoding.
 *
 * 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:
 *
 *        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
 *
 * **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 * 10⁴
 * *   `0 <= data[i] <= 255`
**/
public class Solution {
    public boolean validUtf8(int[] data) {
        int count = 0;
        for (int d : data) {
            if (count == 0) {
                if (d >> 5 == 0b110) {
                    count = 1;
                } else if (d >> 4 == 0b1110) {
                    count = 2;
                } else if (d >> 3 == 0b11110) {
                    count = 3;
                } else if (d >> 7 == 1) {
                    return false;
                }
            } else {
                if (d >> 6 != 0b10) {
                    return false;
                } else {
                    count--;
                }
            }
        }
        return count == 0;
    }
}