Problem Description
You are given a string ss consisting of nn lowercase Latin letters. nn is even.
For each position ii (1≤i≤n1≤i≤n) in string ss you are required to change the letter on this position either to the previous letter in alphabetic order or to the next one (letters 'a' and 'z' have only one of these options). Letter in every position must be changed exactly once.
For example, letter 'p' should be changed either to 'o' or to 'q', letter 'a' should be changed to 'b' and letter 'z' should be changed to 'y'.
That way string "codeforces", for example, can be changed to "dpedepqbft" ('c' →→ 'd', 'o' →→ 'p', 'd' →→ 'e', 'e' →→ 'd', 'f' →→ 'e', 'o' →→ 'p', 'r' →→ 'q', 'c' →→ 'b', 'e' →→ 'f', 's' →→ 't').
String ss is called a palindrome if it reads the same from left to right and from right to left. For example, strings "abba" and "zz" are palindromes and strings "abca" and "zy" are not.
Your goal is to check if it's possible to make string ss a palindrome by applying the aforementioned changes to every position. Print "YES" if string ss can be transformed to a palindrome and "NO" otherwise.
Each testcase contains several strings, for each of them you are required to solve the problem separately.
Input
The first line contains a single integer TT (1≤T≤501≤T≤50) — the number of strings in a testcase.
Then 2T2T lines follow — lines (2i−1)(2i−1) and 2i2i of them describe the ii-th string. The first line of the pair contains a single integer nn (2≤n≤1002≤n≤100, nn is even) — the length of the corresponding string. The second line of the pair contains a string ss, consisting of nn lowercase Latin letters.
Output
Print TT lines. The ii-th line should contain the answer to the ii-th string of the input. Print "YES" if it's possible to make the ii-th string a palindrome by applying the aforementioned changes to every position. Print "NO" otherwise.
Example
input
5 6 abccba 2 cf 4 adfa 8 abaazaba 2 ml
output
YES NO YES NO NO
Note
The first string of the example can be changed to "bcbbcb", two leftmost letters and two rightmost letters got changed to the next letters, two middle letters got changed to the previous letters.
The second string can be changed to "be", "bg", "de", "dg", but none of these resulting strings are palindromes.
The third string can be changed to "beeb" which is a palindrome.
The fifth string can be changed to "lk", "lm", "nk", "nm", but none of these resulting strings are palindromes. Also note that no letter can remain the same, so you can't obtain strings "ll" or "mm".
分析：按照正常的判断回文字符串的方法，只不过再加上判断当前字符的字典序的前一个和后一个。
#include <iostream>
#include <cstring>
using namespace std;
int main(){
char s[110];
int t, m;
cin>>t;
while(t--) {
cin>>m;
cin>>s;
int l = 0, r = m-1;
int flag = 1;
while(l <= r) {
if(s[l]==s[r] || s[l]-1==s[r]-1 || s[l]-1==s[r]+1 || s[l]+1==s[r]-1 || s[l]+1==s[r]+1) { //问题关键所在
l++, r--;
} else {
flag = 0;
break;
}
}
if(flag) {
cout<<"YES"<<endl;
} else {
cout<<"NO"<<endl;
}
}
return 0;
}