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https://github.com/bali182/java-interview-solutions


https://github.com/bali182/java-interview-solutions

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# Java Interview Solutions

This project aims to solve the considerable amount of interview questions, that I have found on [Reddit](http://www.reddit.com/r/cscareerquestions/comments/20ahfq/heres_a_pretty_big_list_of_programming_interview/).

To be on the safe side, here are all the questions:



### General

* Find the most frequent integer in an array [[functional]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/functional/MostFrequentIntegerInArrayFunctional.java) [[iterative]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/iterative/MostFrequentIntegerInArrayIterative.java)

* Find pairs in an integer array whose sum is equal to 10 (bonus: do it in linear time) [[functional]] (https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/functional/PairsWhoseSumIsTenFunctional.java)

* Given 2 integer arrays, determine of the 2nd array is a rotated version of the 1st array. Ex. Original Array A={1,2,3,5,6,7,8} Rotated Array B={5,6,7,8,1,2,3}

* Write fibbonaci iteratively and recursively (bonus: use dynamic programming)[[recursive]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/recursive/FibonacciRecursive.java)

* Find the only element in an array that only occurs once. [[functional]] (https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/functional/ElementThatOnlyOccursOnce.java)

* Find the common elements of 2 int arrays [[iterative]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/iterative/CommonElementsOfTwoArraysIterative.java)

* Implement binary search of a sorted array of integers

* Implement binary search in a rotated array (ex. {5,6,7,8,1,2,3})

* Use dynamic programming to find the first X prime numbers

* Write a function that prints out the binary form of an int

* Implement parseInt [[functional]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/functional/ParseIntFunctional.java)

* Implement squareroot function

* Implement an exponent function (bonus: now try in log(n) time)

* Write a multiply function that multiples 2 integers without using * [[functional]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/functional/MultiplyWithoutOperatorFunctional.java)

* HARD: Given a function rand5() that returns a random int between 0 and 5, implement rand7()

* HARD: Given a 2D array of 1s and 0s, count the number of "islands of 1s" (e.g. groups of connecting 1s)



### Strings

* Find the first non-repeated character in a String

* Reverse a String iteratively and recursively [[iterative]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/iterative/ReverseStringIterative.java) [[recursive]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/recursive/ReverseStringRecursive.java)

* Determine if 2 Strings are anagrams [[iterative]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/iterative/CheckIfTwoStringsAreAnagramsIterative.java)

* Check if String is a palindrome [[iterative]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/iterative/CheckIfPalindromeIterative.java)

* Check if a String is composed of all unique characters [[functional]](https://github.com/bali182/java-interview-solutions/blob/master/src/main/java/com/interview/solution/functional/CheckIfStringHasUniqueCharsFunctional.java)

* Determine if a String is an int or a double

* HARD: Find the shortest palindrome in a String

* HARD: Print all permutations of a String

* HARD: Given a single-line text String and a maximum width value, write the function 'String justify(String text, int maxWidth)' that formats the input text using full-justification, i.e., extra spaces on each line are equally distributed between the words; the first word on each line is flushed left and the last word on each line is flushed right



### Trees

* Implement a BST with insert and delete functions

* Print a tree using BFS and DFS

* Write a function that determines if a tree is a BST

* Find the smallest element in a BST

* Find the 2nd largest number in a BST

* Given a binary tree which is a sum tree (child nodes add to parent), write an algorithm to determine whether the tree is a valid sum tree

* Find the distance between 2 nodes in a BST and a normal binary tree

* Print the coordinates of every node in a binary tree, where root is 0,0

* Print a tree by levels

* Given a binary tree which is a sum tree, write an algorithm to determine whether the tree is a valid sum tree

* Given a tree, verify that it contains a subtree.

* HARD: Find the max distance between 2 nodes in a BST.

* HARD: Construct a BST given the pre-order and in-order traversal Strings



### Stacks, Queues, and Heaps

* Implement a stack with push and pop functions

* Implement a queue with queue and dequeue functions

* Find the minimum element in a stack in O(1) time

* Write a function that sorts a stack (bonus: sort the stack in place without extra memory)

* Implement a binary min heap. Turn it into a binary max heap

* HARD: Implement a queue using 2 stacks



### Linked Lists

* Implement a linked list (with insert and delete functions)

* Find the Nth element in a linked list

* Remove the Nth element of a linked list

* Check if a linked list has cycles

* Given a circular linked list, find the node at the beginning of the loop. Example: A-->B-->C --> D-->E -->C, C is the node that begins the loop

* Check whether a link list is a palindrome

* Reverse a linked list iteratively and recursively



### Sorting

* Implement bubble sort

* Implement selection sort

* Implement insertion sort

* Implement merge sort

* Implement quick sort