ROBOT MEET PROBLEM.

/*
      *  Two robots land with their parachutes on an infinite one-dimensional number line.
      *  They both release their parachutes as soon as they land and start moving.
      *  They are allowed only to make use of the following functions.
      *   I.     moveLeft()         // robot moves to left by 1 unit in 1 unit time
      *   II.    moveRight()        // robot moves to right by 1 unit in 1 unit time
      *   III.   noOperation()      // robot does not move and takes 1 unit time
      *   IV.    onTopOfParachute() // returns true if the robot is standing on top of either of the parachute, else false
      *   V.     didWeMeet()        // returns true if the robot meets to the other robot, else false
      *
      *
      *
      *  Approach -1
      *  __________________________________________________
      *  Move both the robots in oppossite directions.
      *  And at each step check whether 2 robots meet?
      *
      *  WON'T WORK :
      *  Consider robot1 landed at x=0 and robot2 landed at x=100.
      *  case1: move robot1 to right and move robot2 to left then both will meet at x=50.
      *  case2: move robot1 to left and move robot2 to right then they will never meet and will enter into infinite loop.
      *  As we donot have any means of finding out the coordinate of the robots This approach is not reliable.
      *
      *  Approach -2
      *  __________________________________________________
      *  Move both the robot to left.
      *  If robot crosses other's parachute.
      *  Reverse direction of second robot and continue moving first robot in same direction.
      *
      *  WON'T WORK :
      *  Because both robots are executing a separate copy of their program.
      *  A program can only influence robot executing this program and not the other robot as it is executed a copy of same program separately.
      *  And its movements will be governed by that program, variables assigned in one won't work in other.
      *  i.e. it is not possible to change the direction of other robot from program executed by this robot.
      *  
      *  Approach -3
      *  __________________________________________________
      *  follow this pattern, MoveLeft 1 time, MoveRight 2 times, MoveLeft 3 times, MoveRight 4 times and so on.
      *  In each iteration, the robot will go over it's own parachute one time.
      *  But after certain time, one robot will go over its parachute and also the other robots parachute.
      *  At this point, I stop this robot and continue with the other robot.
      *  Finally when this robot go over it's own parachute, it meets the other robot
      *
      *  This will work.
      *
      *  Approach -4
      *  __________________________________________________
      *  Keep a flag whether the robot has reached the other's parachute or not.
      *  If it has reached, call moveLeft() two times, otherwise call moveLeft() and noOperation().
      *  This way one robot will double it's speed as soon as it reaches to the other's parachute and eventually they will meet.
      *
      *  CATCH:
      *  Don't move a robot with twice as speed as other from landing point onwards.
      *  As we donot have any info which robot is behind and which one is in front.
      *  So if front robot is moved with double speed then lagging behind robot then it will never be able to catch it hence, never meet.
*/

      void roboMeet()
      {
            bool reachedParachute = false;
            while( !didWeMeet() )
            {
                  if(reachedParachute)
                  {
                        moveLeft();
                        moveLeft();
                  }
                  else
                  {
                        moveLeft();
                        noOperation();
                  }
                  if( onTopOfParachute() )
                  {
                        reachedParachute = true;
                  }
            }
      }