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// @Title: UTF-8 编码验证 (UTF-8 Validation)
// @Author: 15816537946@163.com
// @Date: 2022-03-13 10:03:03
// @Runtime: 8 ms
// @Memory: 5 MB
const mask1, mask2 = 1 << 7, 1<<7 | 1<<6

func getBytes(num int) int {
    if num&mask1 == 0 {
        return 1
    }
    n := 0
    for mask := mask1; num&mask != 0; mask >>= 1 {
        n++
        if n > 4 {
            return -1
        }
    }
    if n >= 2 {
        return n
    }
    return -1
}

func validUtf8(data []int) bool {
    for index, m := 0, len(data); index < m; {
        n := getBytes(data[index])
        if n < 0 || index+n > m {
            return false
        }
        for _, ch := range data[index+1 : index+n] {
            if ch&mask2 != mask1 {
                return false
            }
        }
        index += n
    }
    return true
}