Robot movement program

Author: Aseem Jain

Diff for: src/codechallenge/medium/RobotMovement.java

@@ -0,0 +1,97 @@
+package codechallenge.medium;
+
+
+import java.io.*;
+        import java.util.*;
+        import java.text.*;
+        import java.math.*;
+        import java.util.regex.*;
+
+/*
+Chewy Debug exercise
+A robot follows instructions to move around.
+
+It can move in four different directions:
+ - North
+ - East
+ - South
+ - West
+
+      N
+      |
+      |
+ W -------- E
+      |
+      |
+      S
+
+There are three different instructions:
+ - F will move the robot forward one step, in the direction it's facing
+ - L will turn the robot counter-clockwise 90 degrees. i.e. if it was facing North, it will now face West
+ - R will turn the robot clockwise 90 degrees, i.e if it was facing North, it will now face East
+
+We have a buggy implementation of isRoundtrip below. Round trip simply means the robot comes back to where it started after following the instructions.
+
+Our goal here is to
+
+- identify and fix the bugs
+- verify the fixes through test cases
+*/
+
+public class RobotMovement {
+    //buggy implementation
+    //sample instructions are: "FFLF", "RFFRFF", etc
+    public static boolean isRoundTrip(String instructions) {
+        int x = 0;
+        int y = 0;
+        //possible values : E (0), N (1), W (2), S (3)
+        int direction = 0;
+
+        for (int i = 0; i < instructions.length(); i++) {
+            switch (instructions.charAt(i)) {
+
+                case 'F':
+                    System.out.println(direction);
+                    if (direction == 0) {
+                        x += 1;
+                    } else if (direction == 1 ) {
+                        y += 1;
+                    } else if (direction == 2) {
+                        x -= 1;
+                    } else if (direction == 3) {
+                        y -= 1;
+                    }
+                    System.out.println("movement = "+ x + ":"+y);
+                    break;
+
+                case 'L':
+                    direction++;
+                    if ( direction >= 4){
+                        direction = 0;
+                    }
+                    break;
+
+                case 'R':
+                    direction = direction - 1;
+                    if (direction < 0) {
+                        direction = 4 - direction;
+                    }
+                    break;
+
+                default:
+                    throw new RuntimeException("Unexpected instruction " + instructions.charAt(i));
+            }
+        }
+        System.out.println(x + " : " + y);
+//        System.out.println(y);
+        return x == 0 && y == 0;
+    }
+
+    public static void main(String[] args) {
+        assert 1 != 1 ;
+        System.out.println( RobotMovement.isRoundTrip("FLFLFLF"));
+          System.out.println( RobotMovement.isRoundTrip("FRFRFRF"));
+          System.out.println( RobotMovement.isRoundTrip("RFFRFFFF"));
+
+    }
+}