Write a program to find maximum subarray sum in an array. Given an array of N elements, find the maximum possible sum of a contiguous subarray. An array can contain both positive and negative values.

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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.

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

int arr1[] = {2, 3, 4, 5, 6};

int arr2[] = {4, 6, 7, 8, 9};

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.

**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.

ii) Insertion Sort

iii) Bubble Sort

iv) Merge Sort

Selection sort, insertion sort and bubble sort are not suitable for large data sets as their **time complexity** is **O(n ^{2})** . 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).

How to find missing number in array of 1 to n. This question is generally asked in technical interviews. The problem statement is something like that. Given an array of numbers from 1 to 100. The **array is sorted**. **One number is missing** from an array. You have to find the missing number from an array. Also there is no duplicates in an array.

Write a stack program in C using an array. Implement a stack data structure using an Array. In this tutorial, We’ll learn about stack data structure and it’s implementation using an array.

C Program to Implement a Stack using Linked List

A Stack is a Data Structure, in which insertion and deletion operations are allowed only at one end. It worked on **LIFO (Last In First Out)** Principle. In LIFO, an element which inserted last must be the first element to be removed.