coding question

Merge two arrays of objects

let first=[
            {uuid: 2, name: 'Darling'},
            {uuid: 3, name: 'Cry-Baby'},
            {uuid: 4, name: 'Snitch'},
            {uuid: 5, name: 'Pawn'}
        ];
 let second= [
            {uuid: 1, role: 'admin'},
            {uuid: 2, role: 'contributor'},
            {uuid: 3, role: 'owner'},
            {uuid: 4, role: 'contributor'}
            ];
//[
// {uuid:1, name: null, role: 'admin'},
// {uuid:2, name: 'Darling', role: 'contributor'},
// {uuid:3, name: 'Cry-Baby', role: 'owner'},
// {uuid:4, name: 'Snitch', role: 'contributor'},
// {uuid:5, name: 'Pawn', role: null}
//]

const mergeArrayObjects = (arr1, arr2) => {
  const res= [];
// start
  for (const obj of arr1) {
    const dup = arr2.find(
      a => a['uuid'] === obj['uuid'],
    );
    if (dup) {
      res.push(Object.assign(obj, dup));
    } else {
      res.push(obj);
    }
  }
  for (const obj of arr2) {
    const dup = res.find(
      a => a['uuid'] === obj['uuid'],
    );
    if (!dup) {
      res.push(obj);
    }
  }
  ///fill

  res.forEach(element => {
    if(!element.hasOwnProperty('name')) {
        element.name=null;
    }
    if(!element.hasOwnProperty('role')) {
        element.role =null;
    }
  });
  res.sort(function(a, b) { 
    return a.uuid - b.uuid;
  });
	console.log(res);
	
  return res;
}

Count array occurs highest

const numbers = [1,3,4,6,9,8,5,4,3,2,1,4,2,1,1,1];
function ca(num) {
	let count =  {};
  num.map(element => {
    //if(count.hasOwnProperty(element)) {
    if (element in count) {
    	count[element]++;
    } else {
    	count[element] = 1;
    }
  })
  let max = 0;
  let cur = 0;
  for(const key in count) {
  	if(count[key] > max) {
    	max = count[key];
      cur = key;
    }
  }
  return cur;
}

ca(numbers);

delete node in inkedlist

top two frequents in array

flattern object/array

function flatten(arr) {
  return arr.reduce((a, b) => {
    // return Array.isArray(b) ? a.concat(flatten(b)) : a.concat(b);
    return a.concat(Array.isArray(b) ? flatten(b) : b);
  }, []);
};

// es6
const flatten = arr =>
  arr.reduce((a, b) => a.concat(Array.isArray(b) ? flatten(b) : b), []);

var foo = 1;
function bar() {
	foo = 10;
	return;
	function foo() {}
}
bar();
alert(foo);

function bar() {
    return foo;
    foo = 10;
    function foo() {}
    var foo = 11;
}
alert(typeof bar());

function foo(){}
delete foo.length;
alert(typeof foo.length);

closure:

Fibonacci closure:

use closure to change loop / use a closure to create a private counter?

closure in callback

Leetcode

1 2sum

3 string/array use map Longest Substring Without Repeating Characters

use a duplicateIndex = [];

15 3sum 3Sum Closest 3Sum With Multiplicity

for loop, left = i+ 1; right = length -1; while(left < right)....if else

20 Valid Parentheses

push ), ], } into array, use pop();

26 Remove Duplicates from Sorted Array

nums.splice(i, 1); i--;

27 Remove Element

nums.splice(i, 1), i--;

33 Search in Rotated Sorted Array

toxic

36 Valid Sudoku

39 Combination Sum

iterative, help(index + 1, array, target - candidates[index]);

46 Permutations

48 Rotate Image

73 Set Matrix Zeroes

80 Remove Duplicates from Sorted Array II

splice(), O(n)

88 Merge Sorted Array

94 Binary Tree Inorder Traversal

102 Binary Tree Level Order Traversal

121 array / dp Best Time to Buy and Sell Stock

tempmin, tempmax, res. for loop ON/// try to use reduce

    let minPrice = +Infinity;

***** 125 Valid Palindrom

let str = s.replace(/\W/g, '').toLowerCase();

144 Binary Tree Preorder Traversal

151 Reverse Words in a String

155 Min Stack

192 Word Frequency

203 Remove Linked List Elements

204 Count Primes

206 Reverse Linked List

238 Product of Array Except Self

268 Missing Number

use sum, reduce get array sum, diff.

283 Move Zeroes

from back to front.

var moveZeroes = function(nums) {       
    for(var i = nums.length;i--;){
        if(nums[i]===0){
            nums.splice(i,1)
            nums.push(0);
        }
    }
};