feat: implement remove method in binary search class

Author: francislagares

src/index.ts

@@ -5,3 +5,4 @@ import './linked-list/LinkedList';
 import './doubly-linked-list/DoublyLinkedList';
 import './stack/StackClass';
 import './queue/QueueClass';
+import './tree/binary-search/BinarySearchTree';

src/tree/binary-search/BinarySearchTree.ts

@@ -55,4 +55,81 @@ export class BinarySearchTree<T> implements BinarySearchTree<T> {
     }
     return null;
   }
+
+  public remove(value: T): boolean {
+    if (!this.root) {
+      return false;
+    }
+    let currentNode = this.root;
+    let parentNode = null;
+    while (currentNode) {
+      if (value < currentNode.value) {
+        parentNode = currentNode;
+        currentNode = currentNode.left;
+      } else if (value > currentNode.value) {
+        parentNode = currentNode;
+        currentNode = currentNode.right;
+      } else if (currentNode.value === value) {
+        // We have a match, get to work!
+
+        // Option 1: No right child:
+        if (currentNode.right === null) {
+          if (parentNode === null) {
+            this.root = currentNode.left;
+          } else {
+            // if parent > current value, make current left child a child of parent
+            if (currentNode.value < parentNode.value) {
+              parentNode.left = currentNode.left;
+
+              // if parent < current value, make left child a right child of parent
+            } else if (currentNode.value > parentNode.value) {
+              parentNode.right = currentNode.left;
+            }
+          }
+
+          // Option 2: Right child which doesnt have a left child
+        } else if (currentNode.right.left === null) {
+          currentNode.right.left = currentNode.left;
+          if (parentNode === null) {
+            this.root = currentNode.right;
+          } else {
+            // if parent > current, make right child of the left the parent
+            if (currentNode.value < parentNode.value) {
+              parentNode.left = currentNode.right;
+
+              // if parent < current, make right child a right child of the parent
+            } else if (currentNode.value > parentNode.value) {
+              parentNode.right = currentNode.right;
+            }
+          }
+
+          // Option 3: Right child that has a left child
+        } else {
+          //find the Right child's left most child
+          let leftmost = currentNode.right.left;
+          let leftmostParent = currentNode.right;
+          while (leftmost.left !== null) {
+            leftmostParent = leftmost;
+            leftmost = leftmost.left;
+          }
+
+          // Parent's left subtree is now leftmost's right subtree
+          leftmostParent.left = leftmost.right;
+          leftmost.left = currentNode.left;
+          leftmost.right = currentNode.right;
+
+          if (parentNode === null) {
+            this.root = leftmost;
+          } else {
+            if (currentNode.value < parentNode.value) {
+              parentNode.left = leftmost;
+            } else if (currentNode.value > parentNode.value) {
+              parentNode.right = leftmost;
+            }
+          }
+        }
+        return true;
+      }
+    }
+  }
 }

src/tree/binary-search/__tests__/BinarySearchTree.test.ts

@@ -42,4 +42,23 @@ describe('Binary Search Tree', () => {
     expect(bst.lookup(6).value).toBe(6);
     expect(bst.lookup(45)).toBeFalsy();
   });
+
+  test.only('remove nodes from tree', () => {
+    const bst = new BinarySearchTree<number>();
+
+    bst.insert(9);
+    bst.insert(4);
+    bst.insert(6);
+    bst.insert(20);
+    bst.insert(170);
+    bst.insert(15);
+    bst.insert(1);
+
+    expect(bst.remove(9)).toBeTruthy();
+    expect(bst.remove(4)).toBeTruthy();
+    expect(bst.remove(170)).toBeTruthy();
+    expect(bst.remove(53)).toBeFalsy();
+    expect(bst.remove(678)).toBeFalsy();
+    expect(bst.remove(138)).toBeFalsy();
+  });
 });

tsconfig.json

@@ -20,7 +20,7 @@
     /* Additional Checks */
     "noUnusedLocals": true /* Report errors on unused locals. */,
     "noUnusedParameters": true /* Report errors on unused parameters. */,
-    "noImplicitReturns": true /* Report error when not all code paths in function return a value. */,
+    "noImplicitReturns": false /* Report error when not all code paths in function return a value. */,
 
     /* Module Resolution Options */
     "esModuleInterop": true /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */,