file system

README.md

@@ -28,6 +28,8 @@ This repo register my evolution in the Cracking The Coding Interview book as I g
 
 [BoggleBoard](https://github.com/brendonmiranda/CrackingTheCodingInterview/blob/main/src/main/java/data/structure/tree/BoggleBoard.java)
 
+[File System Recursion]()
+
 # AWS Challenges
 
 [Review Score](https://github.com/brendonmiranda/CrackingTheCodingInterview/blob/main/src/main/java/aws/ReviewScore.java)

src/main/java/algorithm/recursion/FileSystem.java

@@ -0,0 +1,51 @@
+package algorithm.recursion;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class FileSystem {
+
+    public static class Directory {
+
+        String name;
+        List<Directory> sub = new ArrayList<>();
+        List<String> files = new ArrayList<>();
+
+    }
+
+
+    /**
+     * Recursively search for files in a directory that match the query (either full filename or extension).
+     *
+     * @param directory obj directory
+     * @param query     file name or extension
+     * @return return file full path list. every single place that it was found
+     */
+    public List<String> searchFiles(Directory directory, String query) {
+
+        final List<String> pathsList = new ArrayList<>();
+
+        for (String fileName : directory.files) {
+
+            String[] nameExt = fileName.split("\\.");
+
+            if (query.equals(fileName) || query.substring(1).equals(nameExt[1]))
+                pathsList.add(directory.name + "/" + fileName);
+        }
+
+        if (directory.sub.isEmpty())
+            return pathsList;
+
+        List<String> subPath = new ArrayList<>();
+        for (Directory subdirectory : directory.sub) {
+            subPath.addAll(searchFiles(subdirectory, query));
+        }
+
+        for (String path : subPath) {
+            pathsList.add(directory.name + "/" + path);
+        }
+
+        return pathsList;
+    }
+
+}

src/test/java/algorithm/recursion/FileSystemTest.java

@@ -0,0 +1,52 @@
+package algorithm.recursion;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class FileSystemTest {
+
+    @Test
+    public void test() {
+
+        FileSystem.Directory root = new FileSystem.Directory();
+        root.name = "root";
+
+        FileSystem.Directory folder1 = new FileSystem.Directory();
+        folder1.name = "folder1";
+        folder1.files.add("file1.txt");
+        folder1.files.add("file2.doc");
+
+        FileSystem.Directory subFolder1 = new FileSystem.Directory();
+        subFolder1.name = "subFolder1";
+
+        FileSystem.Directory folder2 = new FileSystem.Directory();
+        folder2.name = "folder2";
+        folder2.sub.add(subFolder1);
+
+        subFolder1.files.add("file3.txt");
+        subFolder1.files.add("file4.jpg");
+
+        folder2.files.add("file5.pdf");
+
+        root.sub.add(folder1);
+        root.sub.add(folder2);
+        root.files.add("file6.txt");
+
+        FileSystem fileSystem = new FileSystem();
+
+        var paths = fileSystem.searchFiles(root, ".txt");
+        Assertions.assertEquals(paths.get(0), "root/file6.txt");
+        Assertions.assertEquals(paths.get(1), "root/folder1/file1.txt");
+        Assertions.assertEquals(paths.get(2), "root/folder2/subFolder1/file3.txt");
+
+        paths = fileSystem.searchFiles(root, ".doc");
+        Assertions.assertEquals(paths.get(0), "root/folder1/file2.doc");
+
+        paths = fileSystem.searchFiles(root, ".jpg");
+        Assertions.assertEquals(paths.get(0), "root/folder2/subFolder1/file4.jpg");
+
+        paths = fileSystem.searchFiles(root, "file5.pdf");
+        Assertions.assertEquals(paths.get(0), "root/folder2/file5.pdf");
+
+    }
+}