Hello Geeks , I am going to discuss important concepts based on array questions . Try to do code by yourself these questions . As i am not going in Algorithms ,so i will explain some basic concepts. These questions are basic for beginners , So if you know solutions of questions then don’t think that it is enough. For any Query, do comment .
Before go into questions , let’s take look about array .
Array is linear indexed based data structure which allocate memory location based on type of data , if it is integer then each cell will allocate memory cell of 4 byte. Let’s take example , I assume that you know about declaration of array .
int arr[] = new int[5] , here we are creating an array of size 5 which will allocate 5 memory locations of 4 bytes , if we want to fetch data then arr[i] will help to fetch it . Rest of information , you can get from https://www.geeksforgeeks.org/ .
Important Basic Concepts :
Qusetion1 : Given an array [1,2,3,4] , you need to change this array by performing following operation , You need to update i_th index with value of multiplication of all elements except itself but constraint is you can not use divide operator here .
Let’s take example , A[1,2,3,4] then updated array will be A[24, 12, 8, 6] . It means that A[0] = A[1] * A[2] * A[3]
A[1] = A[0] * A[2] * A[3]
A[2] = A[0] * A[1] * A[3]
A[3] = A[0] * A[1] * A[2] , This operation you have to perform , so write a program to update this array.
Question2 : Given an array A contains positive integers , you need to find pairs whose sum is divisible by K .
example :- A[1, 3, 6, 7] K= 2
here pairs will be (1, 3), (1, 7), (3, 7) so ans will be 3 because sum of all pairs is divisible by 2.
Question3 : Given an array A and integer d we need to left rotate our array by d times.
example : A[1,0,9,10] d = 3 , We need to left rotate our array by 3 times, So our new rotated array should be A[10,1,0,9] .
after 1rotation
A[0, 9, 10, 1]
after 2rotation
A[9,10, 1, 0]
after 3rotation
A[10, 1, 0, 9] will be our answer….
Question4 : Given an array A ,every element repeats twice but there is only element which occurred once , So find that one element.
example:- A[1, 3, 4, 3, 1] , So answer should be 4 as it is occurred for once.
Question5 : Given two sorted array A and B , we need to merge these two arrays and return new Array contains all elements of A and B in sorted order.
example:- A[0, 2, 4, 7, 9] , B[4, 5, 7, 11, 27] So we have these two arrays and need to merge these two array and return ans[0,2,4,4,5,7,7,9,11,27] as answer.
Question6 : I am doing a variation in qus5 is that , you need to return a new array which contains all elements without duplicacy .
example:- A[0, 2, 4, 7, 9], B[4, 5, 7, 11, 27] So we need to return our ans as ans[0, 2, 4, 5, 7, 9, 11, 27] . It means that you need to return only unique elements which are present in both A and B arrays.
Question7 : Given an array a containing integers , you need to return maximum sum of any sub-array.
example:- A[1, 2, -1, 4, 5, -10, 4] ,here ans will be 1 + 2 + (-1) + 4 + 5 = 11 .
Question8 : Given an array A contain duplicate integers , you need to find the majority element which appears greater than n/2 time where n is length of array.
example: A[1,1,1,2,3,3,1], here majority element is 1 because 1 apprear greater than (7/2)->3.
Question9 : Given an array containing 0s, 1s and 2s , you need to update array so that every 0s , 1s and 2s will come together .
Twist is that you can not use any sorting algorithms on given array.
example: A[0, 0, 1, 2, 2, 0, 1, 2, 0] -> A[0, 0, 0, 0, 1, 1, 2, 2, 2] , here All 0s ,1s and 2s came together and return new update array.
Question10 : Find a triplet in an array whose sum is closest to K .
example: A[-1, 2, 1, -4], K = 1 so ans will be 2 which is very closest to 1.
Get Some useful video resources for solutions….
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This was really helpful….like a written version of all the advices you gave me sir!
Nice and simple explanation
CodeLicious 
Wc Shubhangi.