Codeforces Round #256 (Div. 2/B)/Codeforces448B_Suffix Structures(字符串处理)

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解题报告

四种情况对应下面四组数据。

给两字符串，判断第一个字符串是怎么变到第二个字符串。

automaton 去掉任意字符后成功转换

array 改变任意两字符后成功转换

再者是两个都有和两个都没有

#include <iostream>
#include <cstdio>
#include <cstring>
#include <stdlib.h>
#include <algorithm>
#include <cmath>
using namespace std;int main()
{char str1[110],str2[110];int h1[100],h2[100],i,j;while(cin>>str1>>str2){memset(h1,0,sizeof(h1));j=0;int l1=strlen(str1),l2=strlen(str2);for(i=0; i<l2,j<l1;){if(str2[i]==str1[j]){j++;i++;}else j++;}if(i==l2)cout<<"automaton"<<endl;else{for(i=0; i<l1; i++){h1[str1[i]-'a']++;}for(i=0; i<l2; i++){if(h1[str2[i]-'a'])h1[str2[i]-'a']--;else break;}if(i==l2&&l1==l2){cout<<"array"<<endl;}else if(i==l2&&l1!=l2)cout<<"both"<<endl;else cout<<"need tree"<<endl;}}
}

Suffix Structures

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

Bizon the Champion isn't just a bison. He also is a favorite of the "Bizons" team.

At a competition the "Bizons" got the following problem: "You are given two distinct words (strings of English letters), s and t. You need to transform word s into word t". The task looked simple to the guys because they know the suffix data structures well. Bizon Senior loves suffix automaton. By applying it once to a string, he can remove from this string any single character. Bizon Middle knows suffix array well. By applying it once to a string, he can swap any two characters of this string. The guys do not know anything about the suffix tree, but it can help them do much more.

Bizon the Champion wonders whether the "Bizons" can solve the problem. Perhaps, the solution do not require both data structures. Find out whether the guys can solve the problem and if they can, how do they do it? Can they solve it either only with use of suffix automaton or only with use of suffix array or they need both structures? Note that any structure may be used an unlimited number of times, the structures may be used in any order.

Input

The first line contains a non-empty word s. The second line contains a non-empty word t. Words s and t are different. Each word consists only of lowercase English letters. Each word contains at most 100 letters.

Output

In the single line print the answer to the problem. Print "need tree" (without the quotes) if word s cannot be transformed into word teven with use of both suffix array and suffix automaton. Print "automaton" (without the quotes) if you need only the suffix automaton to solve the problem. Print "array" (without the quotes) if you need only the suffix array to solve the problem. Print "both" (without the quotes), if you need both data structures to solve the problem.

It's guaranteed that if you can solve the problem only with use of suffix array, then it is impossible to solve it only with use of suffix automaton. This is also true for suffix automaton.

Sample test(s) 
input 
automaton
tomat
output 
automaton
input 
array
arary
output 
array
input 
both
hot
output 
both
input 
need
tree
output 
need tree

Note

In the third sample you can act like that: first transform "both" into "oth" by removing the first character using the suffix automaton and then make two swaps of the string using the suffix array and get "hot".

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