Recursion vs Iteration – Difference between Recursion and Iteration

Recursion vs Iteration. What’s the difference between recursion and iteration. Recursion and Iteration both are two different programming approaches. In some cases recursion is best suited and in some other cases iterative way of programming is good.

In programming, repeated set of instructions can be handled either by using recursive or iterative approach in your code. So which approach you choose and why. Let’s talk about recursion vs iteration.

Implementation of Binary Search using Recursion.

Find Common Elements in Two Arrays – Intersection of two Arrays

Given two sorted arrays, Write a code to find common elements in two arrays. In other words, we have to write a code to find the intersection of two arrays.

Find Common Elements in Two Arrays

Let’s assume following two sorted arrays arr1[] and arr2[].

int arr1[] = {2,  3,  4,  5,  6};
int arr2[] = {4,  6,  7,  8,  9};

So the common elements in these two arrays is 4 and 6.

Generate Prime Numbers between 1 to N – Sieve of Eratosthenes

Write an efficient program to generate prime numbers between 1 to N (Where N is 10, 100, 1000 etc). This question can also be asked like this, Generate prime numbers between 1 to 100 or 1 to 10 etc.

Suppose the value of N is 10, So the prime numbers between 1 to 10 is 2, 3, 5, 7.  Now let’s learn the most efficient algorithm (Sieve of Eratosthenes) to generate Prime Numbers between 1 to N. Before solving this program, let’s understand what is a prime number.

Find the Second Largest Number in an Unsorted Array

Write a Program to find the second largest number in an unsorted array. Given an array of unsorted values find the second largest number in an array.

For example – Let’s take an array.

arr[] = { 4, 1, 5, 2, 8, 0, 3, 55}

The second largest element in this array is 8.  So how do you find the second largest number in an array ?  There are multiple ways by which you can solve this problem.

Find Second Largest Number in an Array

Find Second Largest Number in an Array

First Approach : Sort an Array

The simple approach is  to sort an array using sorting algorithm. After sorting an array element at n-2 index will be the second largest element.

You can use following sorting algorithms.

i) Selection Sort

ii) Insertion Sort

iii) Bubble Sort

iv) Merge Sort

v)Quick Sort

Selection sort, insertion sort and bubble sort are not suitable for large data sets as their time complexity is O(n2) . You can use Merge Sort or Quick Sort for large data sets.

NOTE –  If  values of an array is  repeated then this approach won’t work. Then the best approach is to traverse an array to find the second largest element.

Second Approach : Traverse an array

The best approach is to traverse an array to find the second largest number in an array. Using this approach maintain two flags one for highest and other for the second highest number. The time complexity of this approach is O(n).

Top Websites to Learn Coding Online

There is no age for learning and when it comes to learn programming then the online resources are best since you get to know the latest stuff and tricks. Another important reason why you would like learning programming online is that you won’t need any teacher as such and you will in turn save money.So basically which websites are best to learn coding online? We assimilated the 5 best websites from which you can easily learn programming/coding and achieve your purpose.