const union = (...arr) => [...new Set(arr.flat())];

// Example
union([1, 2], [2, 3], [3]);     // [1, 2, 3]

var invertTree = function(root) {
    const reverseNode = node => {
        if (node == null) {
            return null
        }
        reverseNode(node.left);
        reverseNode(node.right);
        let holdLeft = node.left;
        node.left = node.right;
        node.right = holdLeft;
        return node;
    }

    return reverseNode(root);
};

const express = require('express')
const mongoose = require('mongoose')
const cors = require('cors')
const dotenv = require('dotenv')

const server = express()
dotenv.config()


server.use(express.json())




server.get('/' , (req , res)=>{
    res.send('Hello')
})



//4.lancement du serveur
server.listen(process.env.PORT  , ()=>{
    console.log('server run on http://localhost:'+process.env.PORT)
})

class SequentialQueue{	//if you want it to go backwards, too bad
	next(){
		return this.i++;
	}
	constructor(start = 0){
		this.i = start;
	}
}
const que = new SequentialQueue(0);
for(let i = 0; i < 10; i++){
	console.log(que.next());
}

const countSubstrings = (str, searchValue) => {
  let count = 0,
    i = 0;
  while (true) {
    const r = str.indexOf(searchValue, i);
    if (r !== -1) [count, i] = [count + 1, r + 1];
    else return count;
  }
};

countSubstrings('tiktok tok tok tik tok tik', 'tik'); // 3
countSubstrings('tutut tut tut', 'tut'); // 4

function Clock(props) {
  return (
    <div>
      <h1>Hello, world!</h1>
      <h2>It is {props.date.toLocaleTimeString()}.</h2>
    </div>
  );
}

function tick() {
  ReactDOM.render(
    <Clock date={new Date()} />,
    document.getElementById('root')
  );
}

setInterval(tick, 1000);