Competitive Programming #29 : [LineUp]

To prepare his students for an upcoming game, the sports coach decides to try some new training drills. To begin with, he lines them up and starts with the following warm-up exercise: when the coach says 'L', he instructs the students to turn to the left. Alternatively, when he says 'R', they should turn to the right. Finally, when the coach says 'A', the students should turn around.

Unfortunately some students (not all of them, but at least one) can't tell left from right, meaning they always turn right when they hear 'L' and left when they hear 'R'. The coach wants to know how many times the students end up facing the same direction.

Given the list of commands the coach has given, count the number of such commands after which the students will be facing the same direction.

Example

For commands = "LLARL", the output should be
lineUp(commands) = 3.

Let's say that there are 4 students, and the second one can't tell left from right. In this case, only after the second, third and fifth commands will the students face the same direction.

Input/Output

• [execution time limit] 0.5 seconds (cpp)
• [input] string commands
  String consisting of characters 'L', 'R' and 'A' only.
  Guaranteed constraints:
  0 ≤ commands.length ≤ 35.
• [output] integer
  The number of commands after which students face the same direction

Solution:

------------------------------------------------------------

Let's

p- students that do correct turns
l - students that do opposite turns (L -> R, R  ->L)

s - The number of commands after which students face the same direction

Thats all for variables, Next we have this

When the student turn on the clockwise direction
it will increase his value
When  it is opposite (counterclockwise), the value will decrease
and  if value of p and l are divisible by 2 then s++;

So when the students turn left or right  their values always gonna be odd number , forward and back - even number.

With these statements, you will be able to understand the code: