[leetcode] 393. UTF-8 Validation

class Solution {    
    fun validUtf8(data: IntArray): Boolean {
        val size = data.size
        var i = 0
        
        while (i < size) {
            val byte = getByte(data[i])            
            if (byte == -1) return false
            
            for (j in 1 until byte) {
                if (i + j >= size) return false
                // 11000000 => 10000000
                if (data[i + j].and(192) != 128) return false
            }
            i += byte
        }
        return true
    }
    
    fun getByte(value: Int): Int {
        return when {        
            value.and(128) == 0 -> 1 // 10000000 => 00000000            
            value.and(224) == 192 -> 2 // 11100000 => 11000000           
            value.and(240) == 224 -> 3 // 11110000 => 11100000           
            value.and(248) == 240 -> 4 // 11111000 => 11110000 
            else -> -1
        }
    }
}