【leetcode】91. 解码方法

int numDecodings(char * s){
    int f0 = 0, f1=1, f2, i, len = strlen(s);
    for (i = len - 1; i >= 0; i--){
        if (s[i] == ‘0‘)
            f2 = 0;
        else if (s[i] == ‘1‘ || s[i] == ‘2‘&& i+1<len && s[i + 1] - ‘0‘ < 7)
            f2 = f0 + f1;
        else
            f2 = f1;
        f0 = f1;
        f1 = f2;
    }
    return f2;
}