LeetCode in Kotlin
393. UTF-8 Validation
Medium
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
nbits are all one’s, then + 1bit is0, followed byn - 1bytes with the most significant2bits being10.
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 * 1040 <= data[i] <= 255
Solution
class Solution {
fun validUtf8(data: IntArray): Boolean {
var count = 0
for (d in data) {
if (count == 0) {
if (d shr 5 == 6) {
count = 1
} else if (d shr 4 == 14) {
count = 2
} else if (d shr 3 == 30) {
count = 3
} else if (d shr 7 == 1) {
return false
}
} else {
if (d shr 6 != 2) {
return false
} else {
count--
}
}
}
return count == 0
}
}