(s)
return wo_last
:type s: str
    :rtype: int
:type s: str
    :rtype: int
: type s : str : rtype : int
def num_decodings(s):
    """
    :type s: str
    :rtype: int
    """
    if not s or s[0] == "0":
        return 0
    wo_last, wo_last_two = 1, 1
    for i in range(1, len(s)):
        x = wo_last if s[i] != "0" else 0
        y = wo_last_two if int(s[i-1:i+1]) < 27 and s[i-1] != "0" else 0
        wo_last_two = wo_last
        wo_last = x+y
    return wo_last
def num_decodings ( s ) : if not s or s [ 0 ] == "0" : return 0 wo_last , wo_last_two = 1 , 1 for i in range ( 1 , len ( s ) ) : x = wo_last if s [ i ] != "0" else 0 y = wo_last_two if int ( s [ i - 1 : i + 1 ] ) < 27 and s [ i - 1 ] != "0" else 0 wo_last_two = wo_last wo_last = x + y return wo_last