fix(rotations): use built-in root adjustment

• remove unnecessary parameters to helper functions
• use built-in root adjustment of the rotate functions
• swap parameters of the rotation functions, to pass the tree first

Signed-off-by: Matej Focko <mfocko@redhat.com>

avl.js

@@ -33,30 +33,24 @@ class AVLTree extends RankedTree {
         );
     }
 
-    fix0Child(x, y, z, rotatingAroundRoot, rotateLeft, rotateRight) {
+    fix0Child(x, y, z, rotateLeft, rotateRight) {
         let newRoot = x.parent;
 
         if (!y || nodeDifference(y) == 2) {
-            newRoot = rotateRight(z);
+            newRoot = rotateRight(this, z);
-            if (rotatingAroundRoot) {
-                this.root = newRoot;
-            }
             this.record("Fixing 0-child by single rotation: by z", z, newRoot);
 
             z.demote();
             this.record("Fixing 0-child by single rotation: demoting z", z);
         } else if (nodeDifference(y) == 1) {
-            let intermediateRoot = rotateLeft(x);
+            let intermediateRoot = rotateLeft(this, x);
             this.record(
                 "Fixing 0-child by double-rotation: first rotation by x",
                 x,
                 intermediateRoot
             );
 
-            newRoot = rotateRight(z);
+            newRoot = rotateRight(this, z);
-            if (rotatingAroundRoot) {
-                this.root = newRoot;
-            }
             this.record(
                 "Fixing 0-child by double-rotation: second rotation by z",
                 z,
@@ -91,8 +85,6 @@ class AVLTree extends RankedTree {
             return;
         }
 
-        let rotatingAroundRoot = x.parent.parent == null;
-
         let rankDifference = nodeDifference(x);
         if (rankDifference != 0) {
             return;
@@ -101,49 +93,32 @@ class AVLTree extends RankedTree {
         let xParent = x.parent;
 
         if (rankDifference == 0 && x.parent.left === x) {
-            this.fix0Child(
+            this.fix0Child(x, x.right, xParent, rotateLeft, rotateRight);
-                x,
-                x.right,
-                xParent,
-                rotatingAroundRoot,
-                rotateLeft,
-                rotateRight
-            );
         } else if (rankDifference == 0 && x.parent.right === x) {
-            this.fix0Child(
+            this.fix0Child(x, x.left, xParent, rotateRight, rotateLeft);
-                x,
-                x.left,
-                xParent,
-                rotatingAroundRoot,
-                rotateRight,
-                rotateLeft
-            );
         }
     }
 
-    deleteRotate(x, y, leaning, rotatingAroundRoot, rotateLeft, rotateRight) {
+    deleteRotate(x, y, leaning, rotateLeft, rotateRight) {
         let newRoot = x;
 
         let factor = balanceFactor(y);
         switch (factor) {
             case 0:
             case leaning:
-                newRoot = rotateLeft(x);
+                newRoot = rotateLeft(this, x);
                 break;
             default:
-                let intermediateRoot = rotateRight(y);
+                let intermediateRoot = rotateRight(this, y);
                 this.record(
                     "AVL deletion, fixing by double-rotation: by y",
                     y,
                     intermediateRoot
                 );
 
-                newRoot = rotateLeft(x);
+                newRoot = rotateLeft(this, x);
                 break;
         }
-        if (rotatingAroundRoot) {
-            this.root = newRoot;
-        }
         this.record("AVL deletion, fixing by rotation by x", x, newRoot);
 
         [newRoot.left, newRoot.right, newRoot]
@@ -172,7 +147,6 @@ class AVLTree extends RankedTree {
                 return false;
         }
 
-        let rotatingAroundRoot = x.parent == null;
         let [z, leaning, toLeft, toRight] = [
             x.left,
             -1,
@@ -188,14 +162,7 @@ class AVLTree extends RankedTree {
             ];
         }
 
-        return this.deleteRotate(
+        return this.deleteRotate(x, z, leaning, toLeft, toRight);
-            x,
-            z,
-            leaning,
-            rotatingAroundRoot,
-            toLeft,
-            toRight
-        );
     }
 
     deleteRebalance(node, parent) {

node.js

@@ -36,7 +36,7 @@ function nodeDifferences(node) {
     return [r - nodeRank(left), r - nodeRank(right)];
 }
 
-function rotateRight(x, t) {
+function rotateRight(t, x) {
     let parent = x.parent;
     let y = x.left;
     // let z = x.right;
@@ -63,7 +63,7 @@ function rotateRight(x, t) {
     return y;
 }
 
-function rotateLeft(x, t) {
+function rotateLeft(t, x) {
     let parent = x.parent;
     // let y = x.left;
     let z = x.right;

rbt.js

@@ -47,13 +47,13 @@ class RBTree extends RankedTree {
             // ======
             // z’s uncle y is black and z is a right child
             z = p;
-            rotateLeft(p, this);
+            rotateLeft(this, p);
             this.record("Insertion case #2: rotating by parent");
         } else {
             // Case 3
             // ======
             // z’s uncle y is black and z is a left child
-            rotateRight(pp, this);
+            rotateRight(this, pp);
             this.record("Insertion case #3: rotating by grandparent");
         }
 
@@ -89,7 +89,7 @@ class RBTree extends RankedTree {
             // Case 1
             // ======
             // x’s sibling w is red
-            rotateLeft(parent, this);
+            rotateLeft(this, parent);
             this.record("Deletion case #1: rotating by parent", parent);
             w = right(parent);
         }
@@ -107,7 +107,7 @@ class RBTree extends RankedTree {
             // x’s sibling w is black,
             // w’s left child is red, and w’s right child is black
             if (nodeDifference(right(w), w) == BLACK) {
-                rotateRight(w, this);
+                rotateRight(this, w);
                 this.record("Deletion case #3: rotating by w", w);
                 w = right(parent);
             }
@@ -122,7 +122,7 @@ class RBTree extends RankedTree {
             );
             w.rank++;
             this.record("Deletion case #4: coloring w's child", w);
-            rotateLeft(parent, this);
+            rotateLeft(this, parent);
             this.record("Deletion case #4: rotating by parent", parent);
 
             x = this.root;

wavl.js

@@ -21,7 +21,7 @@ class WAVLTree extends AVLTree {
         );
     }
 
-    fixDelete(x, y, z, reversed, rotatingAroundRoot, rotateLeft, rotateRight) {
+    fixDelete(x, y, z, reversed, rotateLeft, rotateRight) {
         let newRoot = x;
         let [v, w] = [y.left, y.right];
 
@@ -30,13 +30,9 @@ class WAVLTree extends AVLTree {
         }
 
         let wDiff = nodeDifference(w, y);
-
         if (wDiff == 1 && y.parent) {
             let oldRoot = y.parent;
-            newRoot = rotateLeft(y.parent);
+            newRoot = rotateLeft(this, y.parent);
-            if (rotatingAroundRoot) {
-                this.root = newRoot;
-            }
             this.record(
                 "Final step of deletion rebalance: single rotation by parent of y",
                 oldRoot,
@@ -58,7 +54,7 @@ class WAVLTree extends AVLTree {
             }
         } else if (wDiff == 2 && v && v.parent) {
             let oldRoot = v.parent;
-            let intermediateRoot = rotateRight(v.parent);
+            let intermediateRoot = rotateRight(this, v.parent);
             this.record(
                 "Final step of deletion rebalance: first of double rotation by parent of v",
                 oldRoot,
@@ -66,10 +62,7 @@ class WAVLTree extends AVLTree {
             );
 
             oldRoot = v.parent;
-            newRoot = rotateLeft(v.parent);
+            newRoot = rotateLeft(this, v.parent);
-            if (rotatingAroundRoot) {
-                this.root = newRoot;
-            }
             this.record(
                 "Final step of deletion rebalance: second of double rotation by parent of v",
                 oldRoot,
@@ -132,8 +125,6 @@ class WAVLTree extends AVLTree {
             return;
         }
 
-        let rotatingAroundRoot = parent.parent == null;
-
         let parentNodeDiffs = nodeDifferences(parent);
         if (parentNodeDiffs.sort().equals([1, 3])) {
             if (parent.left === x) {
@@ -142,7 +133,6 @@ class WAVLTree extends AVLTree {
                     parent.right,
                     parent,
                     false,
-                    rotatingAroundRoot,
                     rotateLeft,
                     rotateRight
                 );
@@ -152,7 +142,6 @@ class WAVLTree extends AVLTree {
                     parent.left,
                     parent,
                     true,
-                    rotatingAroundRoot,
                     rotateRight,
                     rotateLeft
                 );