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how to find number with most divisor from array in java

I got some problem someone of with really helped me but I got program source code who print all of divisor from array, but I tried to print a number with most divisor for ex. array[1,2,3,4,5] and I want to print that the number with most divisor is 4 (1,2,4)
public static class Main {
public static void main(String[] args) {
System.out.println(getNumWithMaxDivisors(numbers));
}
static int getNumDivisors(int n) {
int noOfDivisors = 0;
for (int i = 1; i <= n / 2; i++) {
if (n % i == 0) {
System.out.print(i + " ");
noOfDivisors++;
}
}
return noOfDivisors;
}
static int getNumWithMaxDivisors(int[] numbers) {
int currentMaxDivisors = 0;
int numWithMaxDivisors = numbers[0];
for (int i = 0; i < numbers.length; i++) {
int numDivisors = getNumDivisors(numbers[i]);
if (numDivisors > currentMaxDivisors) {
numWithMaxDivisors = numbers[i];
}
}
return numWithMaxDivisors;
}
}
Code looks that, do you know where is a problem ?

The problem is that inside of your getNumWithMaxDivisors() method, you are not redefining the current number of max divisors. To fix this, you can update it inside of the if statement as so:
static int getNumWithMaxDivisors(int[] numbers) {
int currentMaxDivisors = 0;
int numWithMaxDivisors = numbers[0];
for (int i = 0; i < numbers.length; i++) {
int numDivisors = getNumDivisors(numbers[i]);
if (numDivisors > currentMaxDivisors) {
currentMaxDivisors = numDivisors; //ADD THIS LINE
numWithMaxDivisors = numbers[i];
}
}
return numWithMaxDivisors;
}
Input:
int[] numbers = {1,2,3,4,5};
System.out.println(getNumWithMaxDivisors(numbers));
Output:
4
Side Note: You could just as well start your for loop at i = 2 in your getNumDivisors() method, since every number is divisible by 1, so there is no point in checking it. This just saves you a bit of time!

add this line of code currentMaxDivisors = numDivisors; inside your if-statement like so:
static int getNumWithMaxDivisors(int[] numbers) {
int currentMaxDivisors = 0;
int numWithMaxDivisors = numbers[0];
for (int i = 0; i < numbers.length; i++) {
int numDivisors = getNumDivisors(numbers[i]);
if (numDivisors > currentMaxDivisors) {
currentMaxDivisors = numDivisors; //here this is missing
numWithMaxDivisors = numbers[i];
}
}
return numWithMaxDivisors;
}

Maximum Integer Value java

I was trying to solve the Maximum Integer Value problem form Geeksforgeeks.
The problem states the following:
Given a string S of digits(0-9), your task is to find the maximum value that can be obtained from the string by putting either '*' or '+' operators in between the digits while traversing from left to right of the string and picking up a single digit at a time.
Input:
The first line of input contains T denoting the number of testcases. T testcases follow. Each testcase contains one line of input denoting the string.
Output:
For each testcase, print the maximum value obtained.
this is what I did:
class GFG
{
public static void sort(int[] numbers)
{
int n = numbers.length;
for (int i = 1; i < n; ++i)
{
int key = numbers[i];
int j = i - 1;
while (j >= 0 && numbers[j] > key)
{
numbers[j + 1] = numbers[j];
j = j -1 ;
}
numbers[j + 1] = key;
}
System.out.println(numbers.length - 1);
}
public static void main (String[] args)
{
Scanner sc = new Scanner(System.in);
int testCases = sc.nextInt();
int [] maxNum;
for(int i = 0; i< testCases; i++)
{
String numbers = sc.nextLine();
char[] cNumbers = numbers.toCharArray();
maxNum = new int [cNumbers.length];
for(int j = 0; j + 1 < cNumbers.length; j++)
{
int sum = 0;
int mult = 0;
sum = cNumbers[j] + cNumbers[j + 1];
mult = cNumbers[j] * cNumbers[j + 1];
int maxNumber = Math.max(sum, mult);
maxNum[i] = maxNumber;
}
sort(maxNum);
}
}
}
an example of Input:
2
01230
891
My Output:
-1
4
Correct Output:
9
73
What is wrong with my code?!

Just quick glance it would seem if your digit is less than two it should be added. 2 or larger should get multiplied. Not at a PC to test though.

The idea is to put the operators alternatively and choose the maximum results.
import java.util.Scanner;
public class Demo {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int testCases = Integer.parseInt(sc.nextLine());
for (int i = 0; i < testCases; i++) {
String numbers = sc.nextLine();
int max = 0;
for (int j = 0; j + 1 < numbers.length(); j++) {
int next = Integer.parseInt(numbers.substring(j, j+1));
if (max + next > max * next)
max = max + next;
else
max = max * next;
}
System.out.println(max);
}
sc.close();
}
}

After the execution of
int testCases = sc.nextInt();
the buffer contains a new line character. So when executing the line
String numbers = sc.nextLine();
it read '\n' into numbers, so you got -1 as the first output.
Also you need to convert character to Integer before using it any arithmetic operations.
sum = cNumbers[j] + cNumbers[j+1];
mult = cNumbers[j] * cNumbers[j+1];
So the above code will give you wrong results.
I tried the following sample and worked.
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String inputAsString = sc.nextLine();
int testCases = Integer.parseInt(inputAsString);
int maxNumber = 0;
for (int i = 0; i < testCases; i++) {
String numbers = sc.nextLine();
if(!numbers.matches("\\d+")){
System.out.println("Only numeric values are expected.");
continue;
}
char[] cNumbers = numbers.toCharArray();
int sum = 0;
int mult = 1;
for (int j = 0; j < cNumbers.length; j++) {
int nextNumber = Character.getNumericValue(cNumbers[j]);
sum = sum + nextNumber;
mult = mult * nextNumber;
maxNumber = mult > sum ? mult : sum;
sum = maxNumber;
mult = maxNumber;
}
System.out.println(maxNumber);
}
sc.close();
}

I read your description and what you do is wrong. please read question carefully specially the example in reference site.
as mentioned in comments by moilejter you use sc.nextInt() which doesn't read '\n' and make problem. the next sc.nextLine() will read only a empty string and your program throw exception.
Second problem is that you must calculate max continuously and you don't need an int array (you calculate max result of operation between two successive number and save them in an array which is not correspond to max integer value. you only find max between each two digit but not max of operation on all digit).
Third problem is that you use character as numbers which is made incorrect result. (you must convert them to integer)
So there is a code that works for your output:
public class GFG
{
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int testCases = Integer.valueOf(sc.nextLine());
for (int i = 0; i < testCases; i++)
{
String numbers = sc.nextLine();
char[] cNumbers = numbers.toCharArray();
long maxUntilNow = cNumbers[0] - '0';
for (int j = 1; j < cNumbers.length; j++)
{
int numberOfThisPlace = cNumbers[j] - '0';
maxUntilNow = Math.max(maxUntilNow + numberOfThisPlace,
maxUntilNow * numberOfThisPlace);
}
System.out.println(maxUntilNow);
}
}
}
I hope this is what you want.

As per the problem statement, we need to obtain maximum value from the string by putting either * or + operators in between the digits while traversing from left to right of the string and picking up a single digit at a time.
So, this can be solved in O(n) without using any sorting algorithm.
The simple logic behind the solution is whenever you find "0" or "1" in any of the operands use "+" and the rest of the places use "*".
Here is my solution which got successfully submitted:
import java.util.*;
import java.lang.*;
import java.io.*;
class GFG {
public static void main (String[] args) {
Scanner scan = new Scanner(System.in);
int T = Integer.parseInt(scan.nextLine());
while(T-- > 0) {
String str = scan.nextLine();
maxValue(str);
}
}
static void maxValue(String str) {
long maxNumber = 0;
for(int i = 0; i < str.length(); i++) {
int n = Character.getNumericValue(str.charAt(i));
if (maxNumber == 0 || maxNumber == 1 ||
n == 0 || n == 1) {
maxNumber += n;
} else {
maxNumber *= n;
}
}
System.out.println(maxNumber);
}
}

Function takes a martix (2d array) and prints the max number of the even numbers in each line

I am defining a function to accept a matrix (2d array), for example x[][]; and the function should print the biggest even number in each line
public static void biggestEvenNumOfEachLine(int x[][]){
int even,t=0,max;
int arr[] = new int [x.length];
for(int i = 0; i < x.length;i++){
for(int j = 0; j < x[i].length;j++,t++){
if(x[i][j] % 2 == 0){
even = x[i][j];
arr[j] = even;
}
}
}
}
What am I missing?

I would start by finding the biggest even number in a single line array. Start with the smallest possible value, and then iterate the array. Test for even, and then set the max (and then return it). Something like,
private static int biggestEvenNum(int[] x) {
int max = Integer.MIN_VALUE;
for (int i = 0; i < x.length; i++) {
if (x[i] % 2 == 0) {
max = Math.max(max, x[i]);
}
}
return max;
}
But, in Java 8+, I would prefer to filter for even values and get the max like
private static int biggestEvenNum(int[] x) {
return IntStream.of(x).filter(v -> v % 2 == 0).max().getAsInt();
}
Then your method is as simple as iterating the line(s) in your matrix, printing the result. Like,
public static void biggestEvenNumOfEachLine(int[][] x) {
for (int[] line : x) {
System.out.println(biggestEvenNum(line));
}
}

public static void biggestEvenNumOfEachLine(int x[][])
{
int arr[] = new int [x.length];
for(int i = 0; i < x.length;i++)
for(int j = 0; j < x[i].length;j++)
if(x[i][j] % 2 == 0 && x[i][j] > arr[i]){
arr[i] = x[i][j];
System.out.println(arr[i]);
}
}
This will work but if there is no even number at particular line then corresponding number to that line will be zero.

Calculate factorial of 50 using array only in java

I'm a total beginner of java.
I have a homework to write a complete program that calculates the factorial of 50 using array.
I can't use any method like biginteger.
I can only use array because my professor wants us to understand the logic behind, I guess...
However, he didn't really teach us the detail of array, so I'm really confused here.
Basically, I'm trying to divide the big number and put it into array slot. So if the first array gets 235, I can divide it and extract the number and put it into one array slot. Then, put the remain next array slot. And repeat the process until I get the result (which is factorial of 50, and it's a huge number..)
I tried to understand what's the logic behind, but I really can't figure it out.. So far I have this on my mind.
import java.util.Scanner;
class Factorial
{
public static void main(String[] args)
{
int n;
Scanner kb = new Scanner(System.in);
System.out.println("Enter n");
n = kb.nextInt();
System.out.println(n +"! = " + fact(n));
}
public static int fact(int n)
{
int product = 1;
int[] a = new int[100];
a[0] = 1;
for (int j = 2; j < a.length; j++)
{
for(; n >= 1; n--)
{
product = product * n;
a[j-1] = n;
a[j] = a[j]/10;
a[j+1] = a[j]%10;
}
}
return product;
}
}
But it doesn't show me the factorial of 50.
it shows me 0 as the result, so apparently, it's not working.
I'm trying to use one method (fact()), but I'm not sure that's the right way to do.
My professor mentioned about using operator / and % to assign the number to the next slot of array repeatedly.
So I'm trying to use that for this homework.
Does anyone have an idea for this homework?
Please help me!
And sorry for the confusing instruction... I'm confused also, so please forgive me.
FYI: factorial of 50 is 30414093201713378043612608166064768844377641568960512000000000000

Try this.
static int[] fact(int n) {
int[] r = new int[100];
r[0] = 1;
for (int i = 1; i <= n; ++i) {
int carry = 0;
for (int j = 0; j < r.length; ++j) {
int x = r[j] * i + carry;
r[j] = x % 10;
carry = x / 10;
}
}
return r;
}
and
int[] result = fact(50);
int i = result.length - 1;
while (i > 0 && result[i] == 0)
--i;
while (i >= 0)
System.out.print(result[i--]);
System.out.println();
// -> 30414093201713378043612608166064768844377641568960512000000000000

Her's my result:
50 factorial - 30414093201713378043612608166064768844377641568960512000000000000
And here's the code. I hard coded an array of 100 digits. When printing, I skip the leading zeroes.
public class FactorialArray {
public static void main(String[] args) {
int n = 50;
System.out.print(n + " factorial - ");
int[] result = factorial(n);
boolean firstDigit = false;
for (int digit : result) {
if (digit > 0) {
firstDigit = true;
}
if (firstDigit) {
System.out.print(digit);
}
}
System.out.println();
}
private static int[] factorial(int n) {
int[] r = new int[100];
r[r.length - 1] = 1;
for (int i = 1; i <= n; i++) {
int carry = 0;
for (int j = r.length - 1; j >= 0; j--) {
int x = r[j] * i + carry;
r[j] = x % 10;
carry = x / 10;
}
}
return r;
}
}

How about:
public static BigInteger p(int numOfAllPerson) {
if (numOfAllPerson < 0) {
throw new IllegalArgumentException();
}
if (numOfAllPerson == 0) {
return BigInteger.ONE;
}
BigInteger retBigInt = BigInteger.ONE;
for (; numOfAllPerson > 0; numOfAllPerson--) {
retBigInt = retBigInt.multiply(BigInteger.valueOf(numOfAllPerson));
}
return retBigInt;
}

Please recall basic level of math how multiplication works?
2344
X 34
= (2344*4)*10^0 + (2344*3)*10^1 = ans
2344
X334
= (2344*4)*10^0 + (2344*3)*10^1 + (2344*3)*10^2= ans
So for m digits X n digits you need n list of string array.
Each time you multiply each digits with m. and store it.
After each step you will append 0,1,2,n-1 trailing zero(s) to that string.
Finally, sum all of n listed string. You know how to do that.
So up to this you know m*n
now it is very easy to compute 1*..........*49*50.

how about:
int[] arrayOfFifty = new int[50];
//populate the array with 1 to 50
for(int i = 1; i < 51; i++){
arrayOfFifty[i-1] = i;
}
//perform the factorial
long result = 1;
for(int i = 0; i < arrayOfFifty.length; i++){
result = arrayOfFifty[i] * result;
}
Did not test this. No idea how big the number is and if it would cause error due to the size of the number.
Updated. arrays use ".length" to measure the size.
I now updated result to long data type and it returns the following - which is obviously incorrect. This is a massive number and I'm not sure what your professor is trying to get at.
-3258495067890909184

Sudden infinite loop above certain input argument?

While learning Java I'm redoing some of the Project Euler problems.
This is about Problem 14 - Longest Collatz sequence: https://projecteuler.net/problem=14
My programm runs just fine for a lower CEILING like 1000, but when executed like posted it loops infinitely, I think? What goes wrong here?
public class Test {
public static void main(String[] args) {
int tempMax = 0;
final int CEILING = 1_000_000;
for (int j = 1; j < CEILING; ++j) {
tempMax = Math.max(tempMax, collatzLength(j));
}
System.out.println(tempMax);
}
static int collatzLength(int n) { //computes length of collatz-sequence starting with n
int temp = n;
for (int length = 1; ; ++length) {
if (temp == 1)
return length;
else if (temp % 2 == 0)
temp /= 2;
else
temp = temp * 3 + 1;
}
}
}
Calling System.out.println(collatzLength(1000000)); seperately works just fine so I think we can rule an error here out.

You should use long instead of int. The int overflows while doing your calculations in collatzLength and that causes the infinite loop. From the problem description:
NOTE: Once the chain starts the terms are allowed to go above one million.
The number causing the problem: 113383
The long version gives a result, which is still incorrect because you are printing the length of the longest chain, but you need the number which produces the longest chain.
public static void main(String[] args)
{
int tempMax = 0;
final int CEILING = 1_000_000;
for (int j = 1; j < CEILING; ++j)
{
tempMax = Math.max(tempMax, collatzLength(j));
}
System.out.println(tempMax);
}
static int collatzLength(long n)
{
long temp = n;
for (int length = 1;; ++length)
{
if (temp == 1)
return length;
else if (temp % 2 == 0)
temp /= 2;
else
temp = temp * 3 + 1;
}
}