feat(tree-rotations) leftRightRotation and rightLeftRotation

Author: amejiarosario

src/data-structures/trees/tree-node.js

@@ -23,6 +23,16 @@ class TreeNode {
     return _.cloneDeep(this);
   }
 
+  toValues() {
+    return {
+      value: this.value,
+      left: this.left && this.left.value,
+      right: this.right && this.right.value,
+      parent: this.parent && this.parent.value,
+      parentSide: this.parentSide,
+    };
+  }
+
   get left() {
     return this.descendents[LEFT];
   }

src/data-structures/trees/tree-rotations.js

@@ -1,3 +1,32 @@
+/**
+ * Swap parent's child
+ *
+ *
+ * @example Child on the left side
+ *
+ * p = parent
+ * o = old child
+ * n = new child
+ *
+ * p           p
+ *  \    =>     \
+ *   o           n
+ *
+ * @param {TreeNode} oldChild current child's parent
+ * @param {TreeNode} newChild new child's parent
+ * @param {TreeNode} parent parent
+ */
+function swapParentChild(oldChild, newChild, parent) {
+  if (parent) {
+    const side = oldChild.isParentRightChild ? 'right' : 'left';
+    // this set parent child AND also
+    parent[side] = newChild;
+  } else {
+    // no parent? so set it to null
+    newChild.parent = null;
+  }
+}
+
 /**
  * Single Left Rotation (LL Rotation)
  * @param {TreeNode} node
@@ -6,9 +35,11 @@ function leftRotation(node) {
   const newParent = node.right;
   const grandparent = node.parent;
 
-  newParent.parent = node.parent;
-  if (grandparent) { grandparent.left = newParent; }
+  swapParentChild(node, newParent, grandparent);
+
+  // do LL rotation
   newParent.left = node;
+  node.right = undefined;
 
   return newParent;
 }
@@ -21,9 +52,11 @@ function rightRotation(node) {
   const newParent = node.left;
   const grandparent = node.parent;
 
-  newParent.parent = node.parent;
-  if (grandparent) { grandparent.left = newParent; }
+  swapParentChild(node, newParent, grandparent);
+
+  // do RR rotation
   newParent.right = node;
+  node.left = undefined;
 
   return newParent;
 }
@@ -39,8 +72,15 @@ function leftRightRotation(node) {
   return newParent;
 }
 
+/**
+ * Right Left Rotation (RL Rotation)
+ * @param {TreeNode} node
+ */
 function rightLeftRotation(node) {
-
+  let newParent;
+  newParent = rightRotation(node.right);
+  newParent = leftRotation(node);
+  return newParent;
 }
 
 module.exports = {

src/data-structures/trees/tree-rotations.spec.js

@@ -11,7 +11,6 @@ describe('Tree rotations', () => {
   let n2;
   let n3;
   let n4;
-  let n5;
 
   beforeEach(() => {
     n1 = new TreeNode(1);
@@ -36,9 +35,15 @@ describe('Tree rotations', () => {
       const newParent = leftRotation(n2);
 
       expect(newParent).toBe(n3);
-      expect(n3.left).toBe(n2);
-      expect(n3.right).toBe(n4);
-      expect(n3.parent).toBe(n1);
+      expect(n1.toValues()).toMatchObject({
+        value: 1, left: undefined, right: 3, parent: null,
+      });
+      expect(n2.toValues()).toMatchObject({
+        value: 2, left: undefined, right: undefined, parent: 3,
+      });
+      expect(n3.toValues()).toMatchObject({
+        value: 3, left: 2, right: 4, parent: 1,
+      });
     });
 
     it('should rotate left with root', () => {
@@ -56,9 +61,15 @@ describe('Tree rotations', () => {
       const newParent = leftRotation(n1);
 
       expect(newParent).toBe(n2);
-      expect(n2.left).toBe(n1);
-      expect(n2.right).toBe(n3);
-      expect(n2.parent).toBe(null);
+      expect(n1.toValues()).toMatchObject({
+        value: 1, left: undefined, right: undefined, parent: 2,
+      });
+      expect(n2.toValues()).toMatchObject({
+        value: 2, left: 1, right: 3, parent: null,
+      });
+      expect(n3.toValues()).toMatchObject({
+        value: 3, left: undefined, right: 4, parent: 2,
+      });
     });
 
     it('should rotate last two', () => {
@@ -76,9 +87,15 @@ describe('Tree rotations', () => {
       const newParent = leftRotation(n1);
       expect(newParent).toBe(n2);
 
-      expect(n3.left.value).toBe(2);
-      expect(n2.left.value).toBe(1);
-      expect(n1.left).toBe(undefined);
+      expect(n1.toValues()).toMatchObject({
+        value: 1, left: undefined, right: undefined, parent: 2,
+      });
+      expect(n2.toValues()).toMatchObject({
+        value: 2, left: 1, right: undefined, parent: 3,
+      });
+      expect(n3.toValues()).toMatchObject({
+        value: 3, left: 2, right: undefined, parent: 4,
+      });
     });
   });
 
@@ -98,11 +115,18 @@ describe('Tree rotations', () => {
       const newParent = rightRotation(n3);
 
       expect(newParent).toBe(n2);
-      expect(n2.left).toBe(n1);
-      expect(n2.right).toBe(n3);
-      expect(n2.parent).toBe(n4);
-      expect(n3.parent).toBe(n2);
-      expect(n4.left).toBe(n2);
+      expect(n1.toValues()).toMatchObject({
+        value: 1, left: undefined, right: undefined, parent: 2,
+      });
+      expect(n2.toValues()).toMatchObject({
+        value: 2, left: 1, right: 3, parent: 4,
+      });
+      expect(n3.toValues()).toMatchObject({
+        value: 3, left: undefined, right: undefined, parent: 2,
+      });
+      expect(n4.toValues()).toMatchObject({
+        value: 4, left: 2, right: undefined, parent: null,
+      });
     });
 
     it('should right rotate at the top', () => {
@@ -117,6 +141,32 @@ describe('Tree rotations', () => {
       const newParent = rightRotation(n3);
 
       expect(newParent).toBe(n2);
+      expect(n2.toValues()).toMatchObject({
+        value: 2, left: 1, right: 3, parent: null,
+      });
+    });
+
+    it('should last two', () => {
+      //  1
+      //   \
+      //     3*
+      //   /
+      //  2
+      n1.right = n3;
+      n3.left = n2;
+
+      const newParent = rightRotation(n3);
+
+      expect(newParent).toBe(n2);
+      expect(n1.toValues()).toMatchObject({
+        value: 1, left: undefined, right: 2, parent: null,
+      });
+      expect(n2.toValues()).toMatchObject({
+        value: 2, left: undefined, right: 3, parent: 1,
+      });
+      expect(n3.toValues()).toMatchObject({
+        value: 3, left: undefined, right: undefined, parent: 2,
+      });
     });
   });
 
@@ -136,10 +186,39 @@ describe('Tree rotations', () => {
       const newParent = leftRightRotation(n3);
 
       expect(newParent).toBe(n2);
-      expect(n2.left).toBe(n1);
-      expect(n2.right).toBe(n3);
-      expect(n2.parent).toBe(n4);
-      expect(n4.left).toBe(n2);
+      expect(n1.toValues()).toMatchObject({
+        value: 1, left: undefined, right: undefined, parent: 2,
+      });
+      expect(n2.toValues()).toMatchObject({
+        value: 2, left: 1, right: 3, parent: 4,
+      });
+      expect(n3.toValues()).toMatchObject({
+        value: 3, left: undefined, right: undefined, parent: 2,
+      });
+    });
+  });
+
+  describe('#rightLeftRotation (RL Rotation)', () => {
+    it('should do a RR rotation and then a LL rotation', () => {
+      //  1*
+      //   \
+      //     3
+      //   /
+      //  2
+      n1.right = n3;
+      n3.left = n2;
+
+      const newParent = rightLeftRotation(n1);
+      expect(newParent).toBe(n2);
+      expect(n1.toValues()).toMatchObject({
+        value: 1, left: undefined, right: undefined, parent: 2,
+      });
+      expect(n2.toValues()).toMatchObject({
+        value: 2, left: 1, right: 3, parent: null,
+      });
+      expect(n3.toValues()).toMatchObject({
+        value: 3, left: undefined, right: undefined, parent: 2,
+      });
     });
   });
 });