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Commite6fd223

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Added Array questions and source code
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‎Array/README.md‎

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#Array Manipulation in #"diff-5dd02a5489b8804f74afbcb5673c28fef853bdaf3e0e5edce72f9c2da728941e-empty-2-0" data-selected="false" role="gridcell" tabindex="-1" valign="top">
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###How do you create an empty array in JavaScript?
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```javascript
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constarr= [1,2,3,4,"Hello", {name:"Vishal"}, [1,2,3],4];
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// const arr2 = new Array();
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console.log(arr);
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```
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###How do you access the first and last elements of an array?
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```javascript
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constfirstElement= arr[0];// O(1)
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constarrLength=arr.length;
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constlastElement= arr[arrLength-1];
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console.log(firstElement, arrLength, lastElement);
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```
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###How do you remove the last element from an array?
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```javascript
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constlastElement1=arr.pop();// O(1)
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console.log(arr, lastElement1);
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```
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###How do you add an element to the end of an array?
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```javascript
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arr.push(5);// O(1)
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console.log(arr);
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```
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###How do you add an element to the start of an array?
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```javascript
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arr.unshift(0);// O(N)
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console.log(arr);
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```
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###How do you remove the first element from an array?
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```javascript
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arr.shift();// O(N)
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console.log(arr);
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```
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###How do you loop through an array in JavaScript?
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```javascript
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for (let i=0; i<arr.length; i++){
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console.log(arr[i]);
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}
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arr.forEach((x,i)=> {
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console.log(x);
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});
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for (let xof arr){
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console.log(x);
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}
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```
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###Question 1: How do you check if an element exists in an array?
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```javascript
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constfindElement= (arr,target)=> {
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for (let xof arr){
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if (x=== target){
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returntrue;
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}
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}
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returnfalse;
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}
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console.log(findElement(arr,"Hello"));
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console.log(findElement(arr,"H"));
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console.log(arr.includes("Hello"));
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```
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###Question 2: How do you find the index of an element in an array?
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```javascript
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constfindElementIndex= (arr,target)=> {
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for (let i=0; i<arr.length; i++){
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if (arr[i]=== target){
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return i;
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}
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}
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return-1;
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}
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console.log(findElementIndex(arr,"Hello"));
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console.log(arr.indexOf("Hello"));
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```
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###How to delete, add & update elements from a specific index?
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```javascript
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console.log(arr);
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arr.splice(1,3);
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console.log(arr);
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arr.splice(1,0,2,3,4,5,6);
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console.log(arr);
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arr.splice(1,3,6,7,8);
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console.log(arr);
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```
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###`splice()` vs`slice()`
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```javascript
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constsubArr=arr.slice(1,4);// [start, end)
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console.log(subArr);
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```
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###Shallow Copy of Array
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```javascript
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constarrB= arr;
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arrB.splice(1,4);
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console.log(arrB, arr);
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```
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###Deep Copy of Array
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```javascript
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constarrC= [...arr];
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constarrD=Array.from(arr);
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constarrE=arr.concat();
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arrC.splice(1,4);
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arrD.splice(1,4);
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arrE.splice(1,3);
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console.log(arrC, arrD, arrE, arr);
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```
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###How to concatenate two arrays in JavaScript?
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```javascript
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constnewArr= [...arr,...arrE];
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constnewArr2=arr.concat(arrE);
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console.log(newArr, newArr2);
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```
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###Question 3: How can you check if two arrays are equal?
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```javascript
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constisArrayEqual= (arr1,arr2)=> {
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if (arr1.length!==arr2.length){
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returnfalse;
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}
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for (let i=0; i<arr1.length; i++){
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if (arr1[i]!== arr2[i]){
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returnfalse;
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}
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}
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returntrue;
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// One Line solution
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// return arr1.length === arr2.length && arr1.every((ele, i) => arr1[i] === arr2[i]);
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}
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console.log(isArrayEqual([1,2,3], [1,2,3]));
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```
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###Question 4: How to sort an array in ascending and descending order?
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```javascript
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constx= [1,4,6,0,-9,-5];
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x.sort();// O(NlogN)
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console.log(x);
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x.sort((a,b)=> b- a);
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console.log(x);
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```
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###Question 5: How to reverse an array?
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```javascript
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x.reverse();
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console.log(x);
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```
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###Map, Filter & Reduce
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```javascript
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constnewMapArr=x.map((ele,i)=> ele* ele);
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console.log(newMapArr);
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constpositiveNumbers=x.filter((ele,i)=> ele>0);
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console.log(positiveNumbers);
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constsumOFArr=positiveNumbers.reduce((acc,ele)=> acc+ ele);
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console.log(sumOFArr);
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```
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###Flat:[1, 2, 4, 5, 6, 7, 8, 9]
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```javascript
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consty= [1,2, [4,5, [6,7]],8,9];
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constflattedArray=y.flat(2);
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console.log(flattedArray);
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```
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###`filter()` vs`find()`
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```javascript
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constpositiveNumber=x.find((ele,i)=> ele>0);
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console.log(positiveNumber);
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```
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#Practice Questions
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-[Two Sum](https://leetcode.com/problems/two-sum/)
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-[Majority Element](https://leetcode.com/problems/majority-element/)
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-[Remove Duplicates from sorted array](https://leetcode.com/problems/remove-duplicates-from-sorted-array)
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-[Squares of a Sorted Array](https://leetcode.com/problems/squares-of-a-sorted-array)
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-[Find Pivot Index](https://leetcode.com/problems/find-pivot-index/)
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-[Move Zeroes](https://leetcode.com/problems/move-zeroes)
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-[Remove Element](https://leetcode.com/problems/remove-element)
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-[Max Consecutive Ones](https://leetcode.com/problems/max-consecutive-ones/)

‎Basics/README.md‎

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#Practise Loop, functions & Math Problems
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3-
###Question 1:sum of all natural numbers from 1 to n
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###Question 1:Sum of all natural numbers from 1 to n
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```javascript
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functionsumOfNaturalNumber(num){
@@ -11,12 +11,11 @@ function sumOfNaturalNumber(num){
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return sum;
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}
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console.log(sumOfNaturalNumber(5))//15
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console.log(sumOfNaturalNumber(10))//55
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console.log(sumOfNaturalNumber(8))//36
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console.log(sumOfNaturalNumber(5));//15
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console.log(sumOfNaturalNumber(10));//55
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console.log(sumOfNaturalNumber(8));//36
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```
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###Question 2: Sum of digits of a number
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```javascript
@@ -29,11 +28,10 @@ function sumOfDigits(num){
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return sum;
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}
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console.log(sumOfDigits(1287))//18
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console.log(sumOfDigits(1287));//18
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```
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###Question 3: count the number of digits of a number
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###Question 3: Count the number of digits of a number
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```javascript
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functioncountDigits(num){
@@ -46,31 +44,30 @@ function countDigits(num){
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return count;
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}
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console.log(countDigits(121))//3
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console.log(countDigits(-1211413131))//10
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console.log(countDigits(121));//3
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console.log(countDigits(-1211413131));//10
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```
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###Question 4: Given an integer x, return true if x is a palindrome, and false otherwise.
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A palindrome number is a number that remains the same when digits are reversed
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###Question 4: Check if a number is palindrome
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```javascript
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letisPalindrome=function(x) {
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let copyNum= x, reverseNum=0;
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while(copyNum>0){
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constlastDigit= copyNum%10;
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reverseNum= reverseNum*10+ lastDigit;
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copyNum=Math.floor(copyNum/10)
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constlastDigit= copyNum%10;
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reverseNum= reverseNum*10+ lastDigit;
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copyNum=Math.floor(copyNum/10);
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}
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return x=== reverseNum
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return x=== reverseNum;
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};
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console.log(isPalindrome(121))//true
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console.log(isPalindrome(1234))//false
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console.log(isPalindrome(121));//true
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console.log(isPalindrome(1234));//false
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```
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###Question 5: Find nthfibonacci number
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###Question 5: Find nthFibonacci number
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The Fibonacci numbers, commonly denoted F(n) form a sequence, called the Fibonacci sequence,
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such that each number is the sum of the two preceding ones, starting from 0 and 1.
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}
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return next;
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};
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// Fibonacci Sequence: 0 1 1 2 3 5 8...
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console.log(fib(5))// 5
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console.log(fib(10))//55
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console.log(fib(5));// 5
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console.log(fib(10));//55
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```
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###Question 6: Missing Number
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###Question 6: Missing Number in an Array
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Given an array nums containing n distinct numbers in the range[0, n],
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return the only number in the range that is missing from the array.
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```javascript
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letmissingNumber=function(nums) {
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let sum=0;
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returnnums.length*(nums.length+1)/2- sum;
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};
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// One Line Solution:
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letmissingNumber= (nums)=>nums.length*(nums.length+1)/2-nums.reduce((acc,num)=> num+ acc);
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console.log(missingNumber([3,0,1]))//2
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console.log(missingNumber([9,6,4,2,3,5,7,0,1]))//8
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console.log(missingNumber([3,0,1]));// 2
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console.log(missingNumber([9,6,4,2,3,5,7,0,1]));// 8
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```
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#Practice Questions
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-[Countodd Numbers in an Interval Range](https://leetcode.com/problems/count-odd-numbers-in-an-interval-range/)
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-[CountOdd Numbers in an Interval Range](https://leetcode.com/problems/count-odd-numbers-in-an-interval-range/)
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-[Fizz Buzz](https://leetcode.com/problems/fizz-buzz/)
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-[Power of Two](https://leetcode.com/problems/power-of-two/)
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-[Find Square root of a Number](https://leetcode.com/problems/sqrtx/)
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-[Find Square root of a Number](https://leetcode.com/problems/sqrtx/)

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