s2 (CCO Canadian_Computing_Competition_Senior)
Time limit: 3 seconds | Memory limit: 512 MB | Task type: batch
Algorithms: implementation, string

# Problem S2: Heavy-Light Composition

## Problem Description

In a string containing only lowercase letters of the alphabet (“a” through "z"), we say a letter is *heavy* if it appears more than once in the string, and *light* otherwise.

We will be given a number of strings. For each string, we would like to determine whether the letters of the string alternate between light and heavy.

## Input Specification

The first line of input will consist of two positive integers $T$ and $N$, representing the number of strings and the length of each string.

The next $T$ lines each contain a sequence of $N$ lowercase letters of the alphabet.

The following table shows how the available 15 marks are distributed:

| Marks | Bounds on $T$   | Bounds on $N$   | Other Restrictions                                             |
| :---: | :-------------: | :-------------: | :------------------------------------------------------------- |
|   5   | $2 \le T \le 4$ | $2 \le N \le 4$ | Only the letters “a” and “b” will be used                      |
|   5   | $2 \le T \le 10$ | $2 \le N \le 30$ | None                                                           |
|   2   | $2 \le T \le 100$ | $2 \le N \le 100$ | Only the letter “a” will be heavy; all other letters are light |
|   3   | $2 \le T \le 10000$ | $2 \le N \le 100$ | None                                                           |

## Output Specification

Output $T$ lines, where each line will be either `T` or `F`. If the $i$-th input string does alternate between light and heavy letters, the $i$-th line of output should be `T`; and otherwise, the $i$-th line of output should be `F`.

## Sample Input 1

```
3 4
abcb
bcbb
babc
```

## Output for Sample Input 1

```
T
F
T
```

La version française figure à la suite de la version anglaise.

## Explanation of Output for Sample Input 1

The first string is composed of a light letter, then a heavy letter, then a light letter, and then a heavy letter.

The second string ends in two consecutive heavy letters.

The third string is composed of a heavy letter, then a light letter, then a heavy letter, and then a light letter.

## Sample Input 2

```
2 3
abc
bcb
```

## Output for Sample Input 2

```
F
T
```

## Explanation of Output for Sample Input 2

The first string is composed of all light letters.

The second string is composed of a heavy letter, then a light letter, and then a heavy letter.

La version française figure à la suite de la version anglaise.

Starter code:

Grader code:

Setup script:

Evaluation script: