Problem:
Score : 500 points

Problem Statement

A robot is put at the origin in a two-dimensional plane.
Initially, the robot is facing in the positive x-axis direction.

This robot will be given an instruction sequence s.
s consists of the following two kinds of letters, and will be executed in order from front to back.

F : Move in the current direction by distance 1.

T : Turn 90 degrees, either clockwise or counterclockwise.

The objective of the robot is to be at coordinates (x, y) after all the instructions are executed.
Determine whether this objective is achievable.

Constraints

s consists of F and T.

1 \leq |s| \leq 8 000

x and y are integers.

|x|, |y| \leq |s|

Input

Input is given from Standard Input in the following format:

s
x y

Output

If the objective is achievable, print Yes; if it is not, print No.

Sample Input 1

FTFFTFFF
4 2

Sample Output 1

Yes

The objective can be achieved by, for example, turning counterclockwise in the first T and turning clockwise in the second T.

Sample Input 2

FTFFTFFF
-2 -2

Sample Output 2

Yes

The objective can be achieved by, for example, turning clockwise in the first T and turning clockwise in the second T.

Sample Input 3

FF
1 0

Sample Output 3

No

Sample Input 4

TF
1 0

Sample Output 4

No

Sample Input 5

FFTTFF
0 0

Sample Output 5

Yes

The objective can be achieved by, for example, turning counterclockwise in the first T and turning counterclockwise in the second T.

Sample Input 6

TTTT
1 0

Sample Output 6

No

Solution in Scala (2.11.7) (judge verdict: Runtime Error)

import java.util.Scanner

import scala.collection.mutable
import scala.collection.immutable

object Main {
  def isOdd(num:Int) = num % 2 != 0
  def isEven(num:Int) = num % 2 == 0

  def main(args: Array[String]) = {
    def func(cand:immutable.Set[Int], move:Int):immutable.Set[Int] = {
      var next_cand = new mutable.HashSet[Int]
      for (x <- cand) {
        next_cand += x + move
        next_cand += x - move
      }

      val ret:immutable.Set[Int] = immutable.Set.empty ++ next_cand
      return ret
    }

    val sc = new Scanner(System.in)
    val moves = sc.nextLine().split("T").map(_.length).zipWithIndex
    val x_moves = moves.collect{
      case x if isEven(x._2) => x._1
    }
    val y_moves = moves.collect{
      case x if isOdd(x._2) => x._1
    }

    val xpos_cand = x_moves.tail.foldLeft(Set(x_moves(0)))(func)
    val ypos_cand = y_moves.foldLeft(Set(0))(func)

    val goal = sc.nextLine().split(" ").map(_.toInt)
    if (xpos_cand.contains(goal(0)) &&
      ypos_cand.contains(goal(1)))
      println("Yes")
    else
      println("No")
  }
}