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| 1 | +package codechallenge.medium; |
| 2 | + |
| 3 | + |
| 4 | +import java.io.*; |
| 5 | + import java.util.*; |
| 6 | + import java.text.*; |
| 7 | + import java.math.*; |
| 8 | + import java.util.regex.*; |
| 9 | + |
| 10 | +/* |
| 11 | +Chewy Debug exercise |
| 12 | +A robot follows instructions to move around. |
| 13 | + |
| 14 | +It can move in four different directions: |
| 15 | + - North |
| 16 | + - East |
| 17 | + - South |
| 18 | + - West |
| 19 | + |
| 20 | + N |
| 21 | + | |
| 22 | + | |
| 23 | + W -------- E |
| 24 | + | |
| 25 | + | |
| 26 | + S |
| 27 | + |
| 28 | +There are three different instructions: |
| 29 | + - F will move the robot forward one step, in the direction it's facing |
| 30 | + - L will turn the robot counter-clockwise 90 degrees. i.e. if it was facing North, it will now face West |
| 31 | + - R will turn the robot clockwise 90 degrees, i.e if it was facing North, it will now face East |
| 32 | + |
| 33 | +We have a buggy implementation of isRoundtrip below. Round trip simply means the robot comes back to where it started after following the instructions. |
| 34 | + |
| 35 | +Our goal here is to |
| 36 | + |
| 37 | +- identify and fix the bugs |
| 38 | +- verify the fixes through test cases |
| 39 | +*/ |
| 40 | + |
| 41 | +public class RobotMovement { |
| 42 | + //buggy implementation |
| 43 | + //sample instructions are: "FFLF", "RFFRFF", etc |
| 44 | + public static boolean isRoundTrip(String instructions) { |
| 45 | + int x = 0; |
| 46 | + int y = 0; |
| 47 | + //possible values : E (0), N (1), W (2), S (3) |
| 48 | + int direction = 0; |
| 49 | + |
| 50 | + for (int i = 0; i < instructions.length(); i++) { |
| 51 | + switch (instructions.charAt(i)) { |
| 52 | + |
| 53 | + case 'F': |
| 54 | + System.out.println(direction); |
| 55 | + if (direction == 0) { |
| 56 | + x += 1; |
| 57 | + } else if (direction == 1 ) { |
| 58 | + y += 1; |
| 59 | + } else if (direction == 2) { |
| 60 | + x -= 1; |
| 61 | + } else if (direction == 3) { |
| 62 | + y -= 1; |
| 63 | + } |
| 64 | + System.out.println("movement = "+ x + ":"+y); |
| 65 | + break; |
| 66 | + |
| 67 | + case 'L': |
| 68 | + direction++; |
| 69 | + if ( direction >= 4){ |
| 70 | + direction = 0; |
| 71 | + } |
| 72 | + break; |
| 73 | + |
| 74 | + case 'R': |
| 75 | + direction = direction - 1; |
| 76 | + if (direction < 0) { |
| 77 | + direction = 4 - direction; |
| 78 | + } |
| 79 | + break; |
| 80 | + |
| 81 | + default: |
| 82 | + throw new RuntimeException("Unexpected instruction " + instructions.charAt(i)); |
| 83 | + } |
| 84 | + } |
| 85 | + System.out.println(x + " : " + y); |
| 86 | +// System.out.println(y); |
| 87 | + return x == 0 && y == 0; |
| 88 | + } |
| 89 | + |
| 90 | + public static void main(String[] args) { |
| 91 | + assert 1 != 1 ; |
| 92 | + System.out.println( RobotMovement.isRoundTrip("FLFLFLF")); |
| 93 | + System.out.println( RobotMovement.isRoundTrip("FRFRFRF")); |
| 94 | + System.out.println( RobotMovement.isRoundTrip("RFFRFFFF")); |
| 95 | + |
| 96 | + } |
| 97 | +} |
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