solves simplify path

Author: anishLearnsToCode

README.md

@@ -66,6 +66,7 @@
 |  67  | [Add Binary](https://leetcode.com/problems/add-binary)                                                                                                    |                                         [![Java](assets/java.png)](src/AddBinary.java) [![Python](assets/python.png)](python/add_binary.py)                                          |                                                                                                                                   |
 |  69  | [Sqrt(x)](https://leetcode.com/problems/sqrtx)                                                                                                            |                                              [![Java](assets/java.png)](src/Sqrtx.java) [![Python](assets/python.png)](python/sqrt.py)                                               |                                                                                                                                   |
 |  70  | [Climbing Stairs](https://leetcode.com/problems/climbing-stairs)                                                                                          |                                    [![Java](assets/java.png)](src/ClimbingStairs.java) [![Python](assets/python.png)](python/climbing_stairs.py)                                     |                                                                                                                                   |
+|  71  | [Simplify Path](https://leetcode.com/problems/simplify-path)                                                                                              |                                                                  [![Java](assets/java.png)](src/SimplifyPath.java)                                                                   |                                                                                                                                   |
 |  73  | [Set Matrix Zeroes](https://leetcode.com/problems/set-matrix-zeroes)                                                                                      |                                                                 [![Java](assets/java.png)](src/SetMatrixZeroes.java)                                                                 |                                                                                                                                   |
 |  83  | [Remove Duplicates from Sorted List](https://leetcode.com/problems/remove-duplicates-from-sorted-list)                                                    |                   [![Java](assets/java.png)](src/RemoveDuplicatesFromSortedList.java) [![Python](assets/python.png)](python/remove_duplicates_from_linked_list.py)                   |                                                                                                                                   |
 |  88  | [Merge Sorted Array](https://leetcode.com/problems/merge-sorted-array)                                                                                    |                                  [![Java](assets/java.png)](src/MergeSortedArray.java) [![Python](assets/python.png)](python/merge_sorted_array.py)                                  |                                                                                                                                   |

src/SimplifyPath.java

@@ -0,0 +1,55 @@
+// https://leetcode.com/problems/simplify-path
+// T: O(|path|)
+// S: O(|path|)
+
+import java.util.LinkedList;
+
+public class SimplifyPath {
+    private static final char SLASH = '/';
+    private static final String ROOT = "/";
+    private static final String GO_ONE_LEVEL_UP = "..";
+    private static final String STAY_WHERE_YOU_ARE = ".";
+
+    public String simplifyPath(String path) {
+        final LinkedList<StringBuilder> fragments = new LinkedList<>();
+        StringBuilder current = new StringBuilder();
+        for (int i = 0 ; i < path.length() ; i++) {
+            if (path.charAt(i) == SLASH) {
+                if (!isEmpty(current)) {
+                    addToFragments(current, fragments);
+                    current = new StringBuilder();
+                }
+            } else current.append(path.charAt(i));
+        }
+        if (!isEmpty(current)) addToFragments(current, fragments);
+        return toPath(fragments);
+    }
+
+    private String toPath(LinkedList<StringBuilder> fragments) {
+        if (fragments.isEmpty()) return ROOT;
+        StringBuilder result = new StringBuilder();
+        for (StringBuilder fragment : fragments) {
+            result.append(SLASH).append(fragment);
+        }
+        return result.toString();
+    }
+
+    private void removeLast(LinkedList<StringBuilder> fragments) {
+        if (!fragments.isEmpty()) {
+            fragments.removeLast();
+        }
+    }
+
+    private void addToFragments(StringBuilder current, LinkedList<StringBuilder> fragments) {
+        String currentString = current.toString();
+        if (GO_ONE_LEVEL_UP.equals(currentString)) {
+            removeLast(fragments);
+        } else if (!STAY_WHERE_YOU_ARE.equals(currentString)) {
+            fragments.add(current);
+        }
+    }
+
+    private boolean isEmpty(StringBuilder stringBuilder) {
+        return stringBuilder.length() == 0;
+    }
+}