In recent interviews Walmart has comeup with a good questions which are being asked for Online coding on hacker rank.
We have come up with coding algorithm & logic, so that it can be easy for you to solve coding challenge. Best luck
Walmart Interview Question 1. Given a number N. print in how many ways it can be represented as N = a+b+c+d , 1< =a< =b< =c< = d; 1<=N< = 5000
Walmart Interview Question 2. Given two number l and r (l<=r<=10^6) find most frequent digit among all prime numbers between l and r inclusive. if frequency is same print highest digit.
Lets start immediately.
Solution 1) What you want to find : number of ways a given number can be formatted. so see the observation
Lets DP[n,k] be the number of ways to represent n as sum of k numbers. Then you are looking for DP[n,4].
For N = 4: Only 1 way - 1 + 1 + 1 + 1
For N = 5: Only 1 way - 1 + 1 + 1 + 2
For N = 6: 2 ways - 1 + 1 + 1 + 3
1 + 1 + 2 + 2
For N = 7: 3 ways - 1 + 1 + 1 + 4
1 + 1 + 2 + 3
1 + 2 + 2 + 2
For N = 8: 5 ways - 1 + 1 + 1 + 5
1 + 1 + 2 + 4
1 + 1 + 3 + 3
1 + 2 + 2 + 3
2 + 2 + 2 + 2
So in order to understand this one, lets make Dynamic Programming solution where n = number
k= number of parts here k=4 (a,b,c,d)
DP[n,1] = 1 DP[n,2] = DP[n-2, 2] + DP[n-1,1] DP[n,3] = DP[n-3, 3] + DP[n-1,2] DP[n,4] = DP[n-4, 4] + DP[n-1,3]
So Final DP equation is ==>
DP[n,k] = DP[n-k, k] + DP[n-1,k-1]
Solution 2) We need to find Prime numbers in range [L,R]. and need to find a highest occuring digit and if frequency is same, the highest number is answer.
What can we do for this program is to divide this prog in 3 parts.
1 ) Find prime numbers and store them in Array.
2 ) Create new array from this array with all just digits
ex : prime’s array = [2, 3, 5, 7, 11, 13, 17]
so new Array will be = [2, 3, 5, 7, 1, 1, 1, 3, 1, 7]
3) Find occurrence of each digit like [0,3,1,2,0,1,0,2] (0 comes 0 time, 1 comes 3 times, and so one…)
Now get the highest digit, return its index, if such numbers are more than one, return the highest index.
Coding Soultion :
for Step 1) Use sieve-of-eratosthenes’s code available at http://www.geeksforgeeks.org/sieve-of-eratosthenes/
for Step 2) its simple Array formation, traverse array, % and / each number by 10 and get digits :)
Tips to crack Walmart Interview Questions
Best Interview Preparation books :
When I was preparing for Walmart and Amazon, I have read several book, sites and blogs to prepare for, out which best site, I have already recommended to you guys.There are plenty of books available for Coding interview, out of which I liked these three at best.
a) Data Structure and Algorithms Made Easy by Narasimha Karumanchi ( Ex. Amazon, Microsoft and My Friend) : This book is best for college grads, As this book starts with simple basic fundamentals of data structure and algorithm, and gradually very good and tough questions with explanation this book covers, so basically after completing this book You can think how to use and modify any existing data structure and algorithm for your question.
b) Cracking the Coding interview by Gayle Laakmann McDowell : this book is for good coders and for those who understand reuse of exiting data structure properly, This book contains best logical and complex questions on Data Structure and Algorithm.
Have happy coding amigos
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