# Category: Beginner

## Find the Index from which 0 starts

Objec­tive:  Given an array of integer which 1’s followed by 0’s. Find the starting index of 0. Example: int [] a = {1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0}; First Index from where 0 starts: 10 int [] a = {1,1,1}; ...

## Find the increasing OR decreasing point in an array

Objec­tive:  Given an array of integer which is first increasing then decreasing. Find the element in array from which point it starts decreasing. OR Given an array of integer which is first increasing then decreasing....

## Find the only element in array which appears only once

Objec­tive: Given an array of integers, all the elements are appear twice but one element which appears only once. Write an algorithm to find that element. Example: int [] a = { 1,5,6,2,1,6,4,3,2,5,3}; output:...

## Algorithm to calculate power(k,n).

Objective:  Given two numbers ‘k’ and ‘n’. Write an algorithm to calculate kn. Example: k = 4, n = 5 kn = 45 = 1024 k = 2, n = 3 kn = 23 =...

## Find remainder without using modulo operator

Objec­tive:  Write Given two integers ‘number’ and ‘divisor’, Write an algorithm to find the remainder if ‘number’ is divided by ‘divisor’. Condition: You are not allowed to use modulo or % operator. Example: num =...

## Swap two numbers without using extra variable

Objective:  Write an algorithm to swap two numbers without using extra variable. This is fun puzzle which is asked in the interview. Approach: Example: a = 3, b = 5 a = a + b...

## Number of 1’s in bit representation of a number

Objec­tive:  Write an algorithm to count the number of 1’s in the bit representation in given number. Exam­ple: Number: 6 Output: 2 ( 1 1 0) Number: 11 Output: 3 ( 1 0 1 1)...

## Find the right most unset bit OR zero bit of a number

Objective: Given a number, write and algorithm to find the right most unset bit or zero bit in it (In binary representation). This problem is similar to: Find the right most set bit of...

## Find the right most set bit of a number

Objective: Given a number, write and algorithm  to find the right most set bit in it (In binary representation). Example: Number : 1 Binary representation: 1 Position of right most set bit: 1 Number...

## Find duplicates in an given array in O(n) time and O(1) extra space.

Objective: Given an array of integers, find out duplicates in it. Example: int [] a = {4, 6, 2, 1, 2, 5}; Output: Array has duplicates : 2 int a [] = {1, 6,...

## Find the last non repeating character in a given string.

Objective: Given a string, write an algorithm to find the last non repeating character in it. Example: String input = “algorithms tutorials” Output: ‘u’ String input = “aabbccdd” Output: No repeating character found. Approach:...

## Find the last repeating character in a given string.

Objective: Given a string, write an algorithm to find the last repeating character in it. Example: String input = “horizon tutorials” Output: ‘i’ String input = “algorithms” Output: No repeating character found. Approach: Naive...

## Find the first non repeating character in a given string

Objective: Given a string, write an algorithm to find the first non repeating character in it. Example: String input = ” tutorial horizon” Output: ‘u’ String input = “aabbccadd” Output: No non-repeating character found....

## Find the first repeating character in a given string

Objective: Given a string, write an algorithm to find the first repeating character in it. Example: String input = “horizon tutorials” Output: ‘o’ String input = “algorithms” Output: No repeating character found. Approach: Naive...

## Reverse the given Array without using built in function

Objective: Given a array, write an algorithm to reverse the array. Example: int a[] = {1, 2, 3, 4, 5} Output: {5, 4, 3, 2, 1} Approach: It’s obvious that you cannot use any...