function checkPalindrom(str) { 
  return str == str.split('').reverse().join('');
}

/**
* unique an array 
**/
let unique = function(arr) { 
 let hashTable = {};
 let data = [];
 for(let i=0,l=arr.length;i<l;i++) {
  if(!hashTable[arr[i]]) {
   hashTable[arr[i]] = true;
   data.push(arr[i]);
  }
 }
 return data

}

module.exports = unique; 

function findMaxDuplicateChar(str) { 
 if(str.length == 1) {
  return str;
 }
 let charObj = {};
 for(let i=0;i<str.length;i++) {
  if(!charObj[str.charAt(i)]) {
   charObj[str.charAt(i)] = 1;
  }else{
   charObj[str.charAt(i)] += 1;
  }
 }
 let maxChar = '',
   maxValue = 1;
 for(var k in charObj) {
  if(charObj[k] >= maxValue) {
   maxChar = k;
   maxValue = charObj[k];
  }
 }
 return maxChar;

}

module.exports = findMaxDuplicateChar; 

function bubbleSort(arr) { 
  for(let i = 0,l=arr.length;i<l-1;i++) {
    for(let j = i+1;j<l;j++) { 
     if(arr[i]>arr[j]) {
        let tem = arr[i];
        arr[i] = arr[j];
        arr[j] = tem;
      }
    }
  }
  return arr;
}
module.exports = bubbleSort; 

function quickSort(arr) {

  if(arr.length<=1) {
    return arr;
  }

  let leftArr = [];
  let rightArr = [];
  let q = arr[0];
  for(let i = 1,l=arr.length; i<l; i++) {
    if(arr[i]>q) {
      rightArr.push(arr[i]);
    }else{
      leftArr.push(arr[i]);
    }
  }

  return [].concat(quickSort(leftArr),[q],quickSort(rightArr));
}

module.exports = quickSort; 

function swap(a , b) { 
 b = b - a;
 a = a + b;
 b = a - b;
 return [a,b];
}

module.exports = swap; 

fibo[i] = fibo[i-1]+fibo[i-2]; 

function getFibonacci(n) { 
 var fibarr = [];
 var i = 0;
 while(i<n) {
  if(i<=1) {
   fibarr.push(i);
  }else{
   fibarr.push(fibarr[i-1] + fibarr[i-2])
  }
  i++;
 }

 return fibarr;
}

 function getMaxProfit(arr) {

  var minPrice = arr[0];
  var maxProfit = 0;

  for (var i = 0; i < arr.length; i++) {
    var currentPrice = arr[i];

    minPrice = Math.min(minPrice, currentPrice);

    var potentialProfit = currentPrice - minPrice;

    maxProfit = Math.max(maxProfit, potentialProfit);
  }

  return maxProfit;
}

function randomString(n) { 
 let str = 'abcdefghijklmnopqrstuvwxyz9876543210';
 let tmp = '',
   i = 0,
   l = str.length;
 for (i = 0; i < n; i++) {
  tmp += str.charAt(Math.floor(Math.random() * l));
 }
 return tmp;
}

module.exports = randomString; 

function queryClassName(node, name) { 
 var starts = '(^|[ \n\r\t\f])',
    ends = '([ \n\r\t\f]|$)';
 var array = [],
    regex = new RegExp(starts + name + ends),
    elements = node.getElementsByTagName("*"),
    length = elements.length,
    i = 0,
    element;

  while (i < length) {
    element = elements[i];
    if (regex.test(element.className)) {
      array.push(element);
    }

    i += 1;
  }

  return array;
}

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

}

class BinarySearchTree {

 constructor() {
  this.root = null;
 }

 insert(data) {
  let n = new Node(data, null, null);
  if (!this.root) {
   return this.root = n;
  }
  let currentNode = this.root;
  let parent = null;
  while (1) {
   parent = currentNode;
   if (data < currentNode.data) {
    currentNode = currentNode.left;
    if (currentNode === null) {
     parent.left = n;
     break;
    }
   } else {
    currentNode = currentNode.right;
    if (currentNode === null) {
     parent.right = n;
     break;
    }
   }
  }
 }

 remove(data) {
  this.root = this.removeNode(this.root, data)
 }

 removeNode(node, data) {
  if (node == null) {
   return null;
  }

  if (data == node.data) {
   // no children node
   if (node.left == null && node.right == null) {
    return null;
   }
   if (node.left == null) {
    return node.right;
   }
   if (node.right == null) {
    return node.left;
   }

   let getSmallest = function(node) {
    if(node.left === null && node.right == null) {
     return node;
    }
    if(node.left != null) {
     return node.left;
    }
    if(node.right !== null) {
     return getSmallest(node.right);
    }

   }
   let temNode = getSmallest(node.right);
   node.data = temNode.data;
   node.right = this.removeNode(temNode.right,temNode.data);
   return node;

  } else if (data < node.data) {
   node.left = this.removeNode(node.left,data);
   return node;
  } else {
   node.right = this.removeNode(node.right,data);
   return node;
  }
 }

 find(data) {
  var current = this.root;
  while (current != null) {
   if (data == current.data) {
    break;
   }
   if (data < current.data) {
    current = current.left;
   } else {
    current = current.right
   }
  }
  return current.data;
 }

}

module.exports = BinarySearchTree;