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update README.md BST
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sontran1 committed Mar 13, 2018
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```


### Binary search tree <a name="btree"></a>
### Binary search tree <a name="btree"></a>
![Binary search tree](pics/btree.JPG)
```javascript
const util = require('util')

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

class binarySearchTree {
constructor() { this.root = null }
add(data) { // add node to binary tree
const node = this.root;
if(this.root === null) { this.root = new Node(data) } else {
searchLeaf(node);
function searchLeaf(node) {
if(data < node.data) {
if(node.left === null) { return node.left = new Node(data) }
searchLeaf(node.left);
} else if(data > node.data) {
if(node.right === null) { node.right = new Node(data) }
searchLeaf(node.right);
} else { return null }
}
}
}
findMin() { // find min value in binary tree
let current = this.root;
while(current.left !== null) { current = current.left }
return current.data;
}
findMax() { // find max value in binary tree
let current = this.root;
while(current.right !== null) { current = current.right }
return current.data;
}
exist(data) { // check if a data is in binary tree
let current = this.root;
while(current) {
if(current.data === data) { return true }
else if(current.data > data) { current = current.left }
else { current = current.right }
}
return false
}
remove(data) { // remove a node from binary tree
this.root = removeNode(this.root, data);
function removeNode(node, data) {
if(node == null) { return null } // root node/tree has nothing in it
if(data < node.data) { // not match, move to left
node.left = removeNode(node.left, data);
} else if(data > node.data) { // not match, move to right
node.right = removeNode(node.right, data);
} else { // found matching node
if(node.left === null && node.right === null) { return null } // no children
if(node.left === null) { return node.right } // has right child
if(node.right === null) { return node.left } // has left child
let rightThenFarthestLeft = node.right; // has both left, right child
while(rightThenFarthestLeft.left !== null) {
rightThenFarthestLeft = rightThenFarthestLeft.left;
}
node.data = rightThenFarthestLeft.data;
removeNode(node.right, rightThenFarthestLeft.data);
}
return node;
}
}
findMinHeight(node = this.root) { // get min height of tree
if (node == null) { return -1 }
let left = this.findMinHeight(node.left);
let right = this.findMinHeight(node.right);
if (left < right) { return left + 1 }
else { return right + 1 }
}
findMaxHeight(node = this.root) { // get max height of tree
if (node == null) { return -1 }
let left = this.findMaxHeight(node.left);
let right = this.findMaxHeight(node.right);
if (left < right) { return right + 1 }
else { return left + 1 }
}
isBalanced() { // check if tree is balanced
return (this.findMinHeight() >= this.findMaxHeight() - 1)
}
inOrder() { // traverse tree to array min -> max
if (this.root == null) { return null } else {
var result = new Array();
traverseInOrder(this.root);
return result;
function traverseInOrder(node) {
node.left && traverseInOrder(node.left);
result.push(node.data);
node.right && traverseInOrder(node.right);
}
};
}
bottomUp() { return this.inOrder() } // synonym of inOrder
topDown() { // traverse tree to array max -> min
if (this.root == null) {
return null;
} else {
var result = new Array();
traverseInOrder(this.root);
return result;
function traverseInOrder(node) {
node.right && traverseInOrder(node.right);
result.push(node.data);
node.left && traverseInOrder(node.left);
}
};
}
preOrder() {
if (this.root == null) { return null } else {
var result = new Array();
function traversePreOrder(node) {
result.push(node.data);
node.left && traversePreOrder(node.left);
node.right && traversePreOrder(node.right);
};
traversePreOrder(this.root);
return result;
};
}
postOrder() {
if (this.root == null) { return null } else {
var result = new Array();
function traversePostOrder(node) {
node.left && traversePostOrder(node.left);
node.right && traversePostOrder(node.right);
result.push(node.data);
};
traversePostOrder(this.root);
return result;
}
}
levelOrder() {
let result = [];
let Q = [];
if (this.root != null) {
Q.push(this.root);
while(Q.length > 0) {
let node = Q.shift();
result.push(node.data);
if (node.left != null) {
Q.push(node.left);
};
if (node.right != null) {
Q.push(node.right);
};
};
return result;
} else {
return null;
};
};
}


var myBt = new binarySearchTree();
myBt.add(4);
myBt.add(1);
myBt.add(8);
myBt.add(0.5);
myBt.add(2);
myBt.add(1.6);
myBt.add(2.2);
myBt.add(1.4);
myBt.add(1.7);
//console.log(util.inspect(myBt, {showHidden: false, depth: null}));
// {
// root : {
// data : 4,
// left : {
// data : 1,
// left : {
// data: 0.5,
// left: null,
// right: null
// },
// right : {
// data : 2,
// left : {
// data : 1.6,
// left : {
// data : 1.4,
// left : null,
// right : null
// },
// right : {
// data : 1.7,
// left : null,
// right : null
// }
// },
// right: {
// data: 2.2,
// left: null,
// right: null
// }
// }
// },
// right : {
// data: 8,
// left: null,
// right: null
// }
// }
// }
console.log(myBt.findMin()); // 0.5
console.log(myBt.findMax()); // 8
console.log(myBt.exist(5)); // false
console.log(myBt.exist(2.2)); // true
console.log(myBt.findMinHeight()); // 1
console.log(myBt.findMaxHeight()); // 4
console.log(myBt.inOrder()); // [ 0.5, 1, 1.4, 1.6, 1.7, 2, 2.2, 4, 8 ]
console.log(myBt.bottomUp()); // [ 0.5, 1, 1.4, 1.6, 1.7, 2, 2.2, 4, 8 ]
console.log(myBt.isBalanced()); // false
console.log(myBt.topDown()); // [ 8, 4, 2.2, 2, 1.7, 1.6, 1.4, 1, 0.5 ]
console.log(myBt.preOrder()); // [ 4, 1, 0.5, 2, 1.6, 1.4, 1.7, 2.2, 8 ]
console.log(myBt.postOrder()); // [ 0.5, 1.4, 1.7, 1.6, 2.2, 2, 1, 8, 4 ]
console.log(myBt.levelOrder()); // [ 4, 1, 8, 0.5, 2, 1.6, 2.2, 1.4, 1.7 ]
console.log(myBt.remove(1));
console.log(util.inspect(myBt, {showHidden: false, depth: null}));
// {
// root : {
// data : 4,
// left : {
// data : 1.4,
// left : {
// data : 0.5,
// left : null,
// right : null
// },
// right : {
// data : 2,
// left : {
// data : 1.6,
// left : null,
// right : {
// data : 1.7,
// left : null,
// right : null
// }
// },
// right : {
// data : 2.2,
// left : null,
// right : null
// }
// }
// },
// right : {
// data : 8,
// left : null,
// right : null
// }
// }
// }
```
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