# Category: Beginner

## Convert Integer to Roman

Objective: Given an Integer, write a program to convert it to Roman number. This problem can be stated as “Convert Decimal to Roman String” OR “Convert numeral value to Roman numeral”. Roman Number –...

## Linear Search vs Binary Search

Earlier we have seen linear search and binary search and how these work individually, In this article we will compare these two search algorithms. If you are new to these, please read the prerequisites...

## Count the number of nodes in a given binary tree

Objective: Given a binary tree, write an algorithm to count all the nodes in the tree. Example: Approach: Do postorder traversal. If the root is null return 0. (base case all well for the...

## Longest contiguous character in a given String – O(N) Solution

Objective: Given an input string, write an algorithm to find the longest contiguous character or in other words, find a maximum consecutive character in the string. Example: Input: “aaabbccccddbbaaa” Output: c, count = 4...

## Collatz Conjecture – Steps to transform Number to 1

The Collatz conjecture is a conjecture in mathematics which states that no matter what value of Positive Number N, If the below sequence is followed then, the sequence will always reach 1. If N...

## String to Integer (AtoI – ASCII to Integer)

Objective: Implement atoi, which converts string to an integer. Rules for converting string to an integer. If the string is null or empty, Integer will be 0. The first character of string may represent...

## Find all Prime Numbers less than equal to N | Set 1

Objective: Given a number N, Write a program to find all prime numbers which are between 0 and N. Prime Number : A prime number is a natural number that has exactly two distinct...

## Find third largest element in a given array

Objective: Given an array of integers, write an algorithm to find the third largest element in the array. Example: Int [] a = { 6, 8, 1, 9, 2, 1, 10} Output: Third largest...

## Find duplicates Characters in the given String

Objective: Given a string, write an algorithm to find all the duplicate characters in the string and print its count. Example: Input String: tutorial horizon Output: Duplicate Characters: r – 2 t – 2...

## Java program to find the largest element in array

Objective– Given an array of numbers, write a java program to find the largest element in the given array. Example: int [] a = {1, 5, 3, 9, 2, 8, 2} Largest Element: 9...

## Find three smallest elements in a given array

Objective: Given an array of integers, write an algorithm to find the three smallest elements in the array. Example: Int [] a = { 6, 8, 1, 9, 2, 10}; Output: 1, 2, 6...

## Stack Java Class – Explained

Earlier we saw about Stack and its implementation using Linked List. Java has a built in class for Stack. In this article we will discuss about it in detail. First brief about Stack. What...

## Infix, Postfix and Prefix Notations/Expressions

Infix, Postfix and Prefix notations are most common ways of writing expressions. Infix notation: Example: (A+B) Infix notation is commonly used in arithmetic formula or statements, the operators are written in-between their operands. An...

## Count Set bits in a given Number

Objective: Given a Number, find all the set bits in that number. Example: Number: 23 Set bits: 4 (10111) Number: 15 Set bits: 4 (1111) Number: 21 Set bits: 3 (10101) Approach: Check the...

## Check if array contains all unique or distinct numbers.

Objective: Given an array of integers, write a program to check if array contains all unique numbers. Example: Integer [] arrA = { 1, 2, 3, 6, 4, 9, 8}; Output: Array has all...