Broken Keyboard

题意翻译

有 $t$ 组测试数据，每组数据包含一个正整数 $n$ 和一个长度为 $n$ 且仅包含小写字母的字符串。 一副坏掉的键盘在打字的时候会出现这样的问题：当第奇数次（键盘上任意一个字母键被按下时计为一次）输入字符时，电脑上显示输入了一遍这个字符；当第偶数次输入字符时，电脑上显示输入了两遍这个字符。键盘打字的时候，新输入的字符出现在已有字符串的末尾。 比如，当键盘输入 $\texttt{osu}$ 时，电脑上会显示为 $\texttt{ossu}$。 对于每组数据中的字符串 $s$，如果它能通过使用这副坏掉的键盘打出在电脑上，则输出 `YES`，否则输出 `NO`。

题目描述

Recently, Mishka started noticing that his keyboard malfunctions — maybe it's because he was playing rhythm games too much. Empirically, Mishka has found out that every other time he presses a key, it is registered as if the key was pressed twice. For example, if Mishka types text, the first time he presses a key, exactly one letter is printed; the second time he presses a key, two same letters are printed; the third time he presses a key, one letter is printed; the fourth time he presses a key, two same letters are printed, and so on. Note that the number of times a key was pressed is counted for the whole keyboard, not for each key separately. For example, if Mishka tries to type the word osu, it will be printed on the screen as ossu. You are given a word consisting of $ n $ lowercase Latin letters. You have to determine if it can be printed on Mishka's keyboard or not. You may assume that Mishka cannot delete letters from the word, and every time he presses a key, the new letter (or letters) is appended to the end of the word.

输入输出格式

输入格式

The first line of the input contains one integer $ t $ ( $ 1 \le t \le 100 $ ) — the number of test cases. The first line of the test case contains one integer $ n $ ( $ 1 \le n \le 100 $ ) — the length of the word. The second line of the test case contains a string $ s $ consisting of $ n $ lowercase Latin letters — the word that should be checked.

输出格式

For each test case, print YES if the word $ s $ can be printed on Mishka's keyboard, and NO otherwise.

输入输出样例

输入样例 #1

4
4
ossu
2
aa
6
addonn
3
qwe

输出样例 #1

YES
NO
YES
NO

说明

In the first test case, Mishka can type the word as follows: press o (one letter o appears at the end of the word), then presses s (two letters s appear at the end of the word), and, finally, press u (one letter appears at the end of the word, making the resulting word ossu). In the second test case, Mishka can try typing the word as follows: press a (one letter a appears at the end of the word). But if he tries to press a one more time, two letters a will appear at the end of the word, so it is impossible to print the word using his keyboard. In the fourth test case, Mishka has to start by pressing q. Then, if he presses w, two copies of w will appear at the end of the word, but the third letter should be e instead of w, so the answer is NO.