LeetCode 91.解码方法 Decode Ways

题目 https://leetcode-cn.com/problems/decode-ways/

'A' -> 1
'B' -> 2
...
'Z' -> 26

注意:
'1' -> 'A'
'01' -> 无效

给定一个只包含数字的非空字符串，请计算解码方法的总数。

const char ascii2hex[256] = 
{
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//0-9//should be static??
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//10-19
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//20-29
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//30-39
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0   ,1   ,//40-49
	2   ,3   ,4   ,5   ,6   ,7   ,8   ,9   ,0x3d,0x3d,//50-59
	0x3d,0x3d,0x3d,0x3d,0x3d,10  ,11  ,12  ,13  ,14  ,//60-69
	15  ,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//70-79
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//80-89
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,10  ,11  ,12  ,//90-99
	13  ,14  ,15  ,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//100-109
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//110-119							
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//120-129
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//130-139
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//140-149
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//150-159
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//160-169
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//170-179
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//180-189
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//190-199
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//200-209										
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//210-219
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//220-229
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//230-239
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,0x3d,//240-249
	0x3d,0x3d,0x3d,0x3d,0x3d,0x3d                     //250-255
};

const char count[256] = 
{
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//0-9//should be static??
	0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x01,0x01,0x01,//10-19
	0x01,0x01,0x01,0x01,0x01,0x01,0x00,0x00,0x00,0x00,//20-29
	0x00,0x00,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x00,//30-39
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//40-49
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//50-59
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//60-69
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//70-79
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//80-89
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//90-99
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//100-109
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//110-119							
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//120-129
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//130-139
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//140-149
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//150-159
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//160-169
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//170-179
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//180-189
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//190-199
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//200-209										
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//210-219
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//220-229
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//230-239
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//240-249
	0x00,0x00,0x00,0x00,0x00,0x00                     //250-255
};

int asc2bcd(unsigned char *s,int lens,unsigned char *b)
{
	int i=0,j;
	for(i=0,j=0;i<lens;i+=2,j++)
	{
		b[j] = (unsigned char)(ascii2hex[s[i]]<<4 | ascii2hex[s[i+1]]);
	}
	return j;
}

int numDecodings(char * s){
	int len = strlen(s);
	if(len == 0)    return 0;
	int i=0;
	unsigned char flag;
	int count1=0,count2=0,count3 = 0;
	if(s[0] == '0')
		count1 = 0;
	else
		count1 = 1;
	if(len == 1)
	{
		return count1;
	}
	count2 = 0;
	asc2bcd(s,2,&flag);
	if(count[flag])
		count2 += 1;
	if(s[1] != '0')
		count2 += count1;
	if(len == 2)
	{
		return count2;
	}
	for(i=2;i<len;i++)
	{
		count3 = 0;
		if(s[i] != '0')
			count3 += count2;
		asc2bcd(&s[i-1],2,&flag);
		if(count[flag])
		{
			//printf("flag\n");
			count3 += count1;
		}
		count1 = count2;
		count2 = count3;
	}
	return count3;
}