Implement remove

src/aud/exam/prep/tree/RecursiveOrderedBinaryTreeNodeProcessor.java

@@ -1,5 +1,7 @@
 package aud.exam.prep.tree;
 
+import aud.exam.prep.Pointer;
+
 import java.util.Comparator;
 
 public class RecursiveOrderedBinaryTreeNodeProcessor<V> extends OrderedBinaryTreeNodeProcessor<V> {
@@ -10,12 +12,12 @@ public class RecursiveOrderedBinaryTreeNodeProcessor<V> extends OrderedBinaryTre
     }
 
     @Override
-    public boolean override(BinaryTreeNode<V> pointer, V from, V to, Comparator<V> cmp) {
+    public boolean override(Pointer<BinaryTreeNode<V>> pointer, V from, V to, Comparator<V> cmp) {
         return false;
     }
 
     @Override
-    public boolean overrideAll(BinaryTreeNode<V> pointer, V from, V to, Comparator<V> cmp) {
+    public boolean overrideAll(Pointer<BinaryTreeNode<V>> pointer, V from, V to, Comparator<V> cmp) {
         return false;
     }
 
@@ -29,7 +31,7 @@ public class RecursiveOrderedBinaryTreeNodeProcessor<V> extends OrderedBinaryTre
 
         var c = cmp.compare(v, tree.key);
 
-        if (c <= 0) {
+        if (c < 0 || c == 0 && tree.right != null) {
             tree.left = insert(tree.left, v, cmp);
         } else {
             tree.right = insert(tree.right, v, cmp);
@@ -39,12 +41,83 @@ public class RecursiveOrderedBinaryTreeNodeProcessor<V> extends OrderedBinaryTre
     }
 
     @Override
-    public boolean remove(BinaryTreeNode<V> tree, V v, Comparator<V> cmp) {
+    public boolean remove(Pointer<BinaryTreeNode<V>> pointer, V v, Comparator<V> cmp) {
+        var tree = pointer.deref;
+
+        if (tree == null) {
             return false;
         }
 
+        var c = cmp.compare(v, tree.key);
+
+        if (c == 0) {
+            if (tree.left == null) {
+                pointer.deref = tree.right;
+            } else if (tree.right == null) {
+                pointer.deref = tree.left;
+            } else {
+                tree.key = getReplacementForRemoval(tree.left, tree, false);
+            }
+
+            return true;
+        }
+
+        if (c < 0) {
+            return removeRec(tree.left, v, cmp, tree, false);
+        }
+
+        return removeRec(tree.right, v, cmp, tree, true);
+    }
+
+    private boolean removeRec(BinaryTreeNode<V> node, V v, Comparator<V> cmp, BinaryTreeNode<V> prev, boolean right) {
+        if (node == null) {
+            return false;
+        }
+
+        var c = cmp.compare(v, node.key);
+
+        if (c == 0) {
+            if (node.left == null) {
+                if (right) {
+                    prev.right = node.right;
+                } else {
+                    prev.left = node.right;
+                }
+            } else if (node.right == null) {
+                if (right) {
+                    prev.right = node.left;
+                } else {
+                    prev.left = node.left;
+                }
+            } else {
+                node.key = getReplacementForRemoval(node.left, node, false);
+            }
+
+            return true;
+        }
+
+        if (c < 0) {
+            return removeRec(node.left, v, cmp, node, false);
+        }
+
+        return removeRec(node.right, v, cmp, node, true);
+    }
+
+    private V getReplacementForRemoval(BinaryTreeNode<V> node, BinaryTreeNode<V> prev, boolean right) {
+        if (node.right == null) {
+            if (right) {
+                prev.right = node.left;
+            } else {
+                prev.left = node.left;
+            }
+            return node.key;
+        }
+
+        return getReplacementForRemoval(node.right, node, true);
+    }
+
     @Override
-    public boolean removeAll(BinaryTreeNode<V> tree, V v, Comparator<V> cmp) {
+    public boolean removeAll(Pointer<BinaryTreeNode<V>> tree, V v, Comparator<V> cmp) {
         return false;
     }
 
@@ -153,9 +226,7 @@ public class RecursiveOrderedBinaryTreeNodeProcessor<V> extends OrderedBinaryTre
         }
 
         if (tree.right != null) {
-            if (!check(tree.right, cmp) || cmp.compare(tree.right.key, tree.key) < 0) {
-                return false;
-            }
+            return check(tree.right, cmp) && cmp.compare(tree.right.key, tree.key) >= 0;
         }
 
         return true;

test/aud/exam/prep/tree/OrderedTreeProcessorTest.java

@@ -1,6 +1,7 @@
 package aud.exam.prep.tree;
 
 import aud.exam.prep.ListProvider;
+import aud.exam.prep.Pointer;
 import aud.exam.prep.Tests;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -80,6 +81,40 @@ public abstract class OrderedTreeProcessorTest<T> {
         assertEquals(max, processor.secondMax(t));
     }
 
+    @ParameterizedTest
+    @ArgumentsSource(ListProvider.class)
+    void testThat_removeOfNonExistsIsFalseAndDoesNotModify(List<Integer> list) {
+        T t = asTree(list);
+        list.sort(CMP);
+
+        var p = new Pointer<>(t);
+        assertFalse(processor.remove(p, -1, CMP));
+        assertFalse(processor.remove(p, 999, CMP));
+        t = p.deref;
+
+        assertTrue(processor.check(t, CMP));
+        assertIterableEquals(list, processor.iterate(t));
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ListProvider.class)
+    void testThat_removeOfExistsIsTrueAndDoesModify(List<Integer> list) {
+        T t = asTree(list);
+        list.sort(CMP);
+
+        while (!list.isEmpty()) {
+            var toRemove = list.get(list.size()/2);
+            list.remove(toRemove);
+
+            var p = new Pointer<>(t);
+            assertTrue(processor.remove(p, toRemove, CMP));
+            t = p.deref;
+
+            assertTrue(processor.check(t, CMP));
+            assertIterableEquals(list, processor.iterate(t));
+        }
+    }
+
 
     @ParameterizedTest
     @ArgumentsSource(ListProvider.class)