InterviewQuestions/binarySearchTreeImp.js at master · sertachak/InterviewQuestions · GitHub

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class Node {
  constructor(value){
    this.value = value;
    this.left = null;
    this.right = null;
  }
}

class BinarySearchTree {
  constructor(){
    this.root = null;
  }
  insert(value){
    const newLeaf = new Node( value );
    if(this.root === null ){
      this.root = newLeaf;
    }
    else{
      let currentNode = this.root;
      while( true )
      {
        if( value < currentNode.value )
        {
          if( currentNode.left === null )
          {
            currentNode.left = newLeaf;
            return this;
          }
          else{
            currentNode = currentNode.left;
          }
        }
        else{
          if( currentNode.right === null )
          {
            currentNode.right = newLeaf;
            return this;
          }
          else{
            currentNode = currentNode.right;
          }
        }
      }

    }
  }

    lookup(value){
    if (!this.root) {
      return false;
    }
    let currentNode = this.root;
    while(currentNode){
      if(value < currentNode.value){
        currentNode = currentNode.left;
      } else if(value > currentNode.value){
        currentNode = currentNode.right;
      } else if (currentNode.value === value) {
        return currentNode;
      }
    }
    return null
  }

    remove(value) {
    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;
      }
    }
  }

}

const tree = new BinarySearchTree();
tree.insert(9)
tree.insert(4)
tree.insert(6)
tree.insert(20)
tree.insert(170)
tree.insert(15)
tree.insert(1)
//JSON.stringify(traverse(tree.root))
tree.lookup(15);
tree.lookup(7);


//     9
//  4     20
//1  6  15  170

function traverse(node) {
  const tree = { value: node.value };
  tree.left = node.left === null ? null : traverse(node.left);
  tree.right = node.right === null ? null : traverse(node.right);
  return tree;
}