Sicily 1001

1001. Alphacode

Constraints

Time Limit: 1 secs, Memory Limit: 32 MB

Description

Alice and Bob need to send secret messages to each other and are discussing ways to encode theirmessages: Alice: "Let's just use a very simple code: We'll assign `A' the code word 1, `B' will be 2, and so on down to `Z' being assigned 26." Bob: "That's a
stupid code, Alice. Suppose I send you the word `BEAN' encoded as 25114. You could decode that in many different ways!" Alice: "Sure you could, but what words would you get? Other than `BEAN', you'd get `BEAAD', `YAAD', `YAN', `YKD' and `BEKD'. I think you
would be able to figure out the correct decoding. And why would you send me the word `BEAN' anyway?" Bob: "OK, maybe that's a bad example, but I bet you that if you got a string of length 500 there would be tons of different decodings and with that many you
would find at least two different ones that would make sense." Alice: "How many different decodings?" Bob: "Jillions!"For some reason, Alice is still unconvinced by Bob's argument, so she requires a program that willdetermine how many decodings there can be
for a given string using her code.

Input

Input will consist of multiple input sets. Each set will consist of a single line of digits representing avalid encryption (for example, no line will begin with a 0). There will be no spaces between the digits.An input line of `0' will terminate the input
and should not be processed

Output

For each input set, output the number of possible decodings for the input string. All answers will bewithin the range of a long variable.

Sample Input

25114
1111111111
3333333333
0

Sample Output

6
89
1

题意解释一下。
给出一个数字数列，判断可以组合出多少种字母数列。

#include<iostream>
#include<cstring>
using namespace std;
bool  is_letter(char begin,char end)
{
if(begin>='3') return false;
else if(begin=='2')
{
//	cout<<"end"<<end<<endl;
if(end<='6');
return true;

return false;
}
else if(begin=='0') return false;
else return true;
}
int main()
{
char num[10000];
long long n_way[10000];

while(cin>>num)
{
if(num[0]=='0') break;
memset(n_way,0,sizeof(n_way));
n_way[0]=1;

if(is_letter(num[0],num[1])==1&&num[1]!='0') n_way[1]=2;

else
{
n_way[1]=1;
}
for(int i=2;i<strlen(num);i++)
{
if(num[i]=='0') n_way[i]=n_way[i-2];
else if(is_letter(num[i-1],num[i])==0) n_way[i]=n_way[i-1];
else n_way[i]=n_way[i-1]+n_way[i-2];
}
/*	for(int i=0;i<strlen(num);i++)
{
cout<<n_way[i]<<endl;
}*/
cout<<n_way[strlen(num)-1]<<endl;

}
return 0;
}