Initial data commit

Task/Tree-from-nesting-levels/Java/tree-from-nesting-levels.java

@@ -0,0 +1,45 @@
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public final class TreeNestingLevels {
+
+	public static void main(String[] args) {
+		List<List<Integer>> lists = List.of(
+ 			Arrays.asList(),
+			Arrays.asList( 1, 2, 4 ),
+			Arrays.asList( 3, 1, 3, 1 ),
+			Arrays.asList( 1, 2, 3, 1 ),
+			Arrays.asList( 3, 2, 1, 3 ),
+			Arrays.asList( 3, 3, 3, 1, 1, 3, 3, 3 )
+		);
+		
+		for ( List<Integer> list : lists ) {
+		    List<Object> tree = createTree(list);
+		    System.out.println(list + " --> " + tree);
+		}	
+	}
+	
+	private static List<Object> createTree(List<Integer> list) {
+		return makeTree(list, 0, 1);
+	}	
+	
+	private static List<Object> makeTree(List<Integer> list, int index, int depth) {
+		List<Object> tree = new ArrayList<Object>();
+		int current;
+		
+		while ( index < list.size() && depth <= ( current = list.get(index) ) ) {
+			if ( depth == current ) {
+				tree.add(current);
+				index += 1;
+			} else {
+				tree.add(makeTree(list, index, depth + 1));
+				final int position = list.subList(index, list.size()).indexOf(depth);
+				index += ( position == -1 ) ? list.size() : position;
+			}			
+		}
+		
+		return tree;		
+	}
+	
+}