Everything Automation: Top interview programming questions: Arrays

Wednesday, August 11, 2021

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Java Programs for programming and coding interview

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1. Write a program to swap elements in given array

	public class SwapArrays {

	public static void main(String[] args) {

	int[] arr = {10, 20, 30, 40, 50};
	System.out.println("Original array: "+ Arrays.toString(arr));

	swap(arr, 0, 4);
	System.out.println("Swapped Array: "+ Arrays.toString(arr));
	reverseArray(arr);
	}

	private static void swap(int[] arr, int index1, int index2) {
	int temp = arr[index1];
	arr[index1] = arr[index2];
	arr[index2] = temp;

	}
	}

	Output:
	Original array: [10, 20, 30, 40, 50]
	Swapped Array: [50, 20, 30, 40, 10]

view raw swap.java hosted with ❤ by GitHub

2. Write a program to find maximum element from given array

	public class MaxArray {

	public static void main(String[] args) {
	int[] arr = {12, 54, 32, 89, 100};
	getMaxArray(arr);
	}


	private static int getMaxArray(int[] arr) {
	int max = 0;

	if (arr == null) {
	return -1;
	}

	for (int i = 0; i <= arr.length-1; i++) {
	if (arr[i] > max) {
	max = arr[i];
	}
	}
	System.out.println("Max arrays is: " + max);
	return max;
	}
	}



	Output:
	Max arrays is: 100

view raw MaxArray.java hosted with ❤ by GitHub

3. Write a program to reverse elements in given array

	public class reverse {

	public static void main(String[] args) {
	int[] arr = {1, 2, 3, 4, 5};
	reverseArr(arr);
	System.out.println("Reverse array is: "+Arrays.toString(arr));
	}

	private static void reverseArr(int[] arr) {
	int start =0;
	int end = arr.length-1;

	while (start<end) {
	int temp = arr[start];
	arr[start] = arr[end];
	arr[end] = temp;
	start++;
	end--;
	}
	}
	}

	Output:
	Reverse array is: [5, 4, 3, 2, 1]

view raw ReverseArray.java hosted with ❤ by GitHub

3. Linear search - Write a programe to search an element from Array

	public class linearSearch {

	public static void main(String[] args) {
	int[] arr = {4, 78, 564, 54, 3, 98, 5, -1};
	int a = LinearSearch(arr, 54);
	System.out.println("Element present at index: "+a);
	}


	private static int LinearSearch(int[] arr, int element){
	if (arr == null) {
	return -1;
	}
	for (int index = 0; index < arr.length ; index++) {
	if (element == arr[index]) {
	return index;
	}
	}
	return -1;
	}

	Output:
	Element present at index: 3

view raw linearSearch.java hosted with ❤ by GitHub

4. Find Numbers with Even Number of Digits


	//Given an array nums of integers, return how many of them contain an even number of digits.

	public class EvenDigitLeetCode {
	public static void main(String[] args) {
	int[] nums = {555, 901, 482, 1771};
	int numbers = findNumbers(nums);
	System.out.println(numbers);
	}

	public static int findNumbers(int[] nums) {
	int count = 0;

	for (int num: nums){
	if (contEvenNumber(num)) {
	count++;
	}
	}
	return count;
	}

	private static boolean contEvenNumber(int num) {

	int count = 0;
	int even = 0;

	while (num !=0) {
	count++;
	num = num/10;
	}
	return count %2 ==0;
	}
	}

	output:
	1

	//output : 1, because array contain only one even number of digit i.e 1771

view raw evenDigit.java hosted with ❤ by GitHub

5. Binary Search - Write a programe to search an element from Array (O(log n) runtime complexity)

	package com.BinarySearch;

	//Leet code 704 - Binary Search

	public class BinarySrch {

	public static void main(String[] args) {
	int[] arr = {-1,0,3,5,9,12};
	int i = search(arr, 5);
	System.out.println(i);
	}

	public static int search(int[] arr, int target){
	int start = 0;
	int end = arr.length - 1;

	while (start <= end) {
	int mid = start + (end - start) / 2;
	if (target < arr[mid]) {
	end = mid - 1;
	} else if (target > arr[mid]) {
	start = mid + 1;
	}else{
	return mid;
	}
	}
	return -1;
	}
	}

	Output: 3

view raw BinarySrch.java hosted with ❤ by GitHub

6. Two number Sum or Check for pair in an array with a given sum

	package com.BinarySearch.BinarySearchPorblems;

	import java.util.Arrays;

	//Check for pair in an array with a given sum - Interview Problem
	//https://afteracademy.com/blog/check-for-pair-in-an-array-with-a-given-sum

	public class SearchElement {

	public static void main(String[] args) {
	int[] arr = {-5, 1, -40, 20, 6, 8, 7};
	System.out.println(getValue(arr,15 ));

	}

	//Using two pointer technique
	static boolean getValue(int[] arr, int target){
	int start = 0;
	int end = arr.length - 1;
	while (start <= end) {
	Arrays.sort(arr);
	if (arr[start] + arr[end] == target) {
	return true;
	}else if(arr[start] + arr[end] > target){
	end--;
	}else{
	start++;
	}
	}
	return false;
	}

	}

view raw SearchElement.java hosted with ❤ by GitHub

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