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Code_Regina

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Tree Traversal

                   -Intro to Tree Traversal
                   -Breadth First Search
                   -Depth First PreOrder
                   -Depth First PostOrder
                   -Depth First InOrder
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Intro to Tree Traversal

There are two ways for tree traversal.
Breadth first search and depth first search

Breadth First Search

Steps to take for breadth first search

  1. Create a queue (can be an array) and a variable to store the values of nodes visited.
  2. Place the root node in the queue.
  3. Loop as long as there is anything in the queue. -Dequeue a node from the queue and push the value of the node into the variable that stores the node. -If there is a left property on the node then dequeue add it to the queue. -If there is a right property on the node then dequeue - add it to the queue. -return the variable that stores the value.

class BinarySearchTree {
    constructor(){
        this.root = null;
    }
    insert(value){
        var newNode = new Node(value);
        if(this.root === null){
            this.root = newNode;
            return this;
        }
        var current = this.root;
        while(true){
            if(value === current.value) return undefined;
            if(value < current.value){
                if(current.left === null){
                    current.left = newNode;
                    return this;
                }
                current = current.left;
            } else {
                if(current.right === null){
                    current.right = newNode;
                    return this;
                } 
                current = current.right;
            }
        }
    }
    find(value){
        if(this.root === null) return false;
        var current = this.root,
            found = false;
        while(current && !found){
            if(value < current.value){
                current = current.left;
            } else if(value > current.value){
                current = current.right;
            } else {
                found = true;
            }
        }
        if(!found) return undefined;
        return current;
    }
    contains(value){
        if(this.root === null) return false;
        var current = this.root,
            found = false;
        while(current && !found){
            if(value < current.value){
                current = current.left;
            } else if(value > current.value){
                current = current.right;
            } else {
                return true;
            }
        }
        return false;
    }
    BFS(){
        var node = this.root,
            data = [],
            queue = [];
        queue.push(node);

        while(queue.length){
           node = queue.shift();
           data.push(node.value);
           if(node.left) queue.push(node.left);
           if(node.right) queue.push(node.right);
        }
        return data;
    }
}




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Depth First PreOrder

Steps to take for Depth first preorder search

  1. Create a variable to store the values of nodes visited.
  2. Store the root of the BST in a variable called current.
  3. Write a helper function which accepts a node. -Push the value of the node to the variable that stores the values. -If the node has a left property, call the helper function with the left property on the node. -If the node has a right property, call the helper function with the right property on the node. Invoke the helper function with the current variable.

 DFSPreOrder(){
        var data = [];
        function traverse(node){
            data.push(node.value);
            if(node.left) traverse(node.left);
            if(node.right) traverse(node.right);
        }
        traverse(this.root);
        return data;
    }

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Depth First PostOrder

Steps to take for Depth first postorder search

  1. Create a variable to store the values of nodes visited.
  2. Store the root of the BST in a variable called current.
  3. Write a helper function which accepts a node. -Push the value of the node to the variable that stores the values. -If the node has a left property, call the helper function with the left property on the node. -If the node has a right property, call the helper function with the right property on the node. Invoke the helper function with the current variable.

    DFSPostOrder(){
        var data = [];
        function traverse(node){
            if(node.left) traverse(node.left);
            if(node.right) traverse(node.right);
            data.push(node.value);
        }
        traverse(this.root);
        return data;
    }

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Depth First InOrder

Steps to take for Depth first inorder search

  1. Create a variable to store the values of nodes visited.
  2. Store the root of the BST in a variable called current.
  3. Write a helper function which accepts a node. -Push the value of the node to the variable that stores the values. -If the node has a left property, call the helper function with the left property on the node. -If the node has a right property, call the helper function with the right property on the node. Invoke the helper function with the current variable.
    DFSInOrder(){
        var data = [];
        function traverse(node){
            if(node.left) traverse(node.left);
            data.push(node.value);
            if(node.right) traverse(node.right);
        }
        traverse(this.root);
        return data;
    }
}

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