[力扣] 算法 393 (C#)

393. UTF-8 编码验证

public class Solution
{
    public bool ValidUtf8(int[] data)
    {
        var itor = new IntArrItor(data);
        while (itor.MoveNext())
        {
            var type = Foo(itor);
            if (type < 0) return false;
            for (var i = 0; i < type; i++)
                if (!itor.MoveNext() || (itor >> 6 ^ 0b10) != 0) return false;
        }
        return true;
    }

    static int Foo(int num)
    {
        if ((num >> 3 ^ 0b11110) == 0) return 3;
        if ((num >> 4 ^ 0b1110) == 0) return 2;
        if ((num >> 5 ^ 0b110) == 0) return 1;
        if ((num >> 7 ^ 0b0) == 0) return 0;
        return -1;
    }

    class IntArrItor : IEnumerator<int>
    {
        int[] arr;
        int curr = -1;
        public IntArrItor(int[] arr) => this.arr = arr;

        public int Current => arr[curr];

        object IEnumerator.Current => Current;

        public void Dispose() { }

        public bool MoveNext() => ++curr < arr.Length;

        public void Reset() => curr = -1;
        public static implicit operator int(IntArrItor itor) => itor.Current;
    }
}