check if set of moves is circular

Author: ZapDos7

README.md

@@ -38,6 +38,7 @@
 - [x] [Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/)
 - [x] [Palindromic Substrings](https://leetcode.com/problems/palindromic-substrings/)
 - [x] [Valid Parentheses](https://leetcode.com/problems/valid-parentheses)
+- [x] [Check if given set of moves is circular or not](http://www.techiedelight.com/check-given-set-moves-circular-not/)
 
 ### Dates
 
@@ -313,7 +314,6 @@
     - [ ] [Greedy coloring of graph](http://www.techiedelight.com/greedy-coloring-graph/)
 
 - LinkedLists
-    - [ ] [Reverse a LL](https://leetcode.com/problems/reverse-linked-list/)
     - [ ] [Detect Cycle](https://leetcode.com/problems/linked-list-cycle/)
     - [ ] [Merge 2 Sorted](https://leetcode.com/problems/merge-two-sorted-lists/)
     - [ ] [Merge k Sorted](https://leetcode.com/problems/merge-k-sorted-lists/)
@@ -384,7 +384,6 @@
     - [ ] [Find path from source to destination in a matrix that satisfies given constraints](http://www.techiedelight.com/find-path-source-destination-matrix-satisfies-given-constraints/)
 - Strings
     - [ ] [KMP](https://www.wikiwand.com/en/articles/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm)
-    - [ ] [Check if given set of moves is circular or not](http://www.techiedelight.com/check-given-set-moves-circular-not/)
     - [ ] [Check if given string is a rotated palindrome or not](http://www.techiedelight.com/check-given-string-rotated-palindrome-not/)
     - [ ] [Check if repeated subsequence is present in the string or not](http://www.techiedelight.com/check-repeated-subsequence-present-string-not/)
     - [ ] [Check if strings can be derived from each other by circularly rotating them](http://www.techiedelight.com/check-strings-can-derived-circularly-rotating/)

src/strings/circularMoves/CircularMoves.java

@@ -0,0 +1,79 @@
+package strings.circularMoves;
+
+import utils.InputReader;
+
+public class CircularMoves {
+
+    static int x = 0;
+    static int y = 0;
+    static Direction direction = Direction.N; // start looking at north
+
+    public static void main(String[] args) {
+        // input
+        System.out.print("Print set of moves: M for same direction, L for left, R for right: ");
+        String moves = InputReader.readLine();
+
+        // validate input
+        if (!moves.matches("^[LMR]*$\n")) {
+            System.err.println("Invalid input");
+        }
+
+        // check
+        if (isCircular(moves.toUpperCase().trim())) {
+            System.out.println("Set of moves " + moves + " is circular");
+        } else {
+            System.out.println("Set of moves " + moves + " is NOT circular");
+        }
+    }
+
+    // start at 0,0, facing UP
+    private static boolean isCircular(String moves) {
+        for (char c : moves.toCharArray()) {
+            switch (c) {
+                case 'L':
+//                    System.out.println("going Left");
+                    if (direction.equals(Direction.N)) {
+                        direction = Direction.W;
+                    } else if (direction.equals(Direction.W)) {
+                        direction = Direction.S;
+                    } else if (direction.equals(Direction.S)) {
+                        direction = Direction.E;
+                    } else if (direction.equals(Direction.E)) {
+                        direction = Direction.N;
+                    }
+                    break;
+                case 'R':
+//                    System.out.println("going right");
+                    if (direction.equals(Direction.N)) {
+                        direction = Direction.E;
+                    } else if (direction.equals(Direction.E)) {
+                        direction = Direction.S;
+                    } else if (direction.equals(Direction.S)) {
+                        direction = Direction.W;
+                    } else if (direction.equals(Direction.W)) {
+                        direction = Direction.N;
+                    }
+                    break;
+                case 'M':
+//                    System.out.println("going forward");
+                    if (direction.equals(Direction.N)) {
+                        y++;
+                    } else if (direction.equals(Direction.S)) {
+                        y--;
+                    } else if (direction.equals(Direction.E)) {
+                        x++;
+                    } else if (direction.equals(Direction.W)) {
+                        x--;
+                    }
+                    break;
+                default: // will never reach here
+                    System.err.println("Invalid set of moves");
+            }
+        }
+        return (x == 0 && y == 0); // if eventually we're back at 0,0, it is circular
+    }
+
+    private enum Direction {
+        N, E, S, W;
+    }
+}