[min_max] fixed bwd search and added tests

src/datastructures/min_max.rs

@@ -329,10 +329,14 @@ impl MinMax {
                     top_down = false;
                     block_search = true;
                 } else {
-                    if self.heap[current_node as usize * 2 + 2].max_excess - self.heap[current_node as usize * 2 + 2].min_excess >= look_for.abs()
+                    if self.heap[current_node as usize * 2 + 2].max_excess
+                        - self.heap[current_node as usize * 2 + 2].min_excess
+                        >= look_for.abs()
                     {
                         current_node = current_node * 2 + 2;
-                        } else if self.heap[current_node as usize * 2 + 1].max_excess - self.heap[current_node as usize * 2 + 1].min_excess >= look_for.abs()
+                    } else if self.heap[current_node as usize * 2 + 1].max_excess
+                        - self.heap[current_node as usize * 2 + 1].min_excess
+                        >= look_for.abs()
                     {
                         current_node = current_node * 2 + 1;
                     } else {