2013
11-10

# Alphacode

Alice and Bob need to send secret messages to each other and are discussing ways to encode their messages:

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 will determine how many decodings there can be for a given string using her code.

Input will consist of multiple input sets. Each set will consist of a single line of digits representing a valid 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

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

25114
1111111111
3333333333
0

6
89
1

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import java.io.*;
public class Main
{
public static void main(String[] args) throws IOException
{
while(true)
{
if(s.equals("0")) break;
int l=s.length();
int[] arr=new int[l];
int count=0;
for(int i=0;i< l-1;i++)
{
if(s.charAt(i+1)!='0')
arr[count++]=s.charAt(i)-'0';
else {
arr[count++]=(s.charAt(i)-'0')*10;
i++;
}
}
if(s.charAt(l-1)!='0') arr[count++]=s.charAt(l-1)-'0';
int[] arr2=new int[count+1];
arr2[count-1]=arr2[count]=1;
for(int i=count-2;i>=0;i--)
{
if((arr[i]*10+arr[i+1]>26)||arr[i+1]>9) arr2[i]=arr2[i+1];
else{
arr2[i]=arr2[i+1]+arr2[i+2];
}
}
System.out.println(arr2[0]);
}
}
}

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2. 我没看懂题目
2
5 6 -1 5 4 -7
7 0 6 -1 1 -6 7 -5
我觉得第一个应该是5 6 -1 5 4 输出是19 5 4
第二个是7 0 6 -1 1 -6 7输出是14 7 7
不知道题目例子是怎么得出来的