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| 118 | |
| Mutant Flatworld Explorers | |
| Robotics, robot motion planning, and machine learning are areas that cross the boundaries of many of | |
| the subdisciplines that comprise Computer Science: artificial intelligence, algorithms and complexity, | |
| electrical and mechanical engineering to name a few. | |
| In addition, robots as “turtles” (inspired by | |
| work by Papert, Abelson, and diSessa) and as “beeper-pickers” (inspired by work by Pattis) have been | |
| studied and used by students as an introduction to programming for many years. | |
| This problem involves determining the position of a robot exploring a pre-Columbian flat world. | |
| Given the dimensions of a rectangular grid and a sequence of robot positions and instructions, you | |
| are to write a program that determines for each sequence of robot positions and instructions the final | |
| position of the robot. | |
| A robot position consists of a grid coordinate (a pair of integers: x-coordinate followed by y- | |
| coordinate) and an orientation (N,S,E,W for north, south, east, and west). A robot instruction is a string | |
| of the letters ‘L’, ‘R’, and ‘F’ which represent, respectively, the instructions: | |
| • Left: the robot turns left 90 degrees and remains on the current grid point. | |
| • Right: the robot turns right 90 degrees and remains on the current grid point. | |
| • Forward: the robot moves forward one grid point in the direction of the current orientation and | |
| mantains the same orientation. | |
| The direction North corresponds to the direction from grid point (x, y) to grid point (x, y + 1). | |
| Since the grid is rectangular and bounded, a robot that moves “off” an edge of the grid is lost forever. | |
| However, lost robots leave a robot “scent” that prohibits future robots from dropping off the world at | |
| the same grid point. The scent is left at the last grid position the robot occupied before disappearing | |
| over the edge. An instruction to move “off” the world from a grid point from which a robot has been | |
| previously lost is simply ignored by the current robot. | |
| Input | |
| The first line of input is the upper-right coordinates of the rectangular world, the lower-left coordinates | |
| are assumed to be 0,0. | |
| The remaining input consists of a sequence of robot positions and instructions (two lines per robot). | |
| A position consists of two integers specifying the initial coordinates of the robot and an orientation | |
| (N,S,E,W), all separated by white space on one line. A robot instruction is a string of the letters ‘L’, ‘R’, | |
| and ‘F’ on one line. | |
| Each robot is processed sequentially, i.e., finishes executing the robot instructions before the next | |
| robot begins execution. | |
| Input is terminated by end-of-file. | |
| You may assume that all initial robot positions are within the bounds of the specified grid. The | |
| maximum value for any coordinate is 50. All instruction strings will be less than 100 characters in | |
| length. | |
| Output | |
| For each robot position/instruction in the input, the output should indicate the final grid position and | |
| orientation of the robot. If a robot falls off the edge of the grid the word ‘LOST’ should be printed after | |
| the position and orientation. | |
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| Sample Input | |
| 5 3 | |
| 1 1 E | |
| RFRFRFRF | |
| 3 2 N | |
| FRRFLLFFRRFLL | |
| 0 3 W | |
| LLFFFLFLFL | |
| Sample Output | |
| 1 1 E | |
| 3 3 N LOST | |
| 2 3 S |