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;
}
Related
For school, i have to build myself a method in java that compresses an array using RLE(run-length encoding). I can't find a solution online because my teacher wants me to solve the problem myself. I, unfortunately, cannot do this for i am a busy man with some busy plans.
RLE turns this: {1,1,1,1,2,2,3,3,6,6,6,7,8,8,8}
into this: {4,1,2,2,2,3,3,6,1,7,3,8}
it basically makes a new array that follows this formula {# of this value, this value, # of this value, this value, cont...} there are 4 1's so {4,1} you get my drift.
Here is what i tried to do(forgive me for my crappy code, i am merely a high school student):
public class tester{
public static void main(String[] args){
int[] potato = {1,1,1,2,2,4,4,4,6,6,6,6};
printArray(compress(potato));
}
public static void printArray(int[] arr){
for(int i = 0; i < arr.length; i++){
System.out.println(arr[i]);
}
}
public static int[] compress(int[] a) {
//figure out how many different numbers there are.
int diffNums = 1;
for(int i = 0; i < a.length; i++){
if(i != a.length-1 && a[i] != a[i+1]){
diffNums++;
}
}
//make compressed array at the correct length.
int[] compressed = new int[diffNums * 2];
//figure out what each number is.
int[] nums = new int[diffNums];
nums[0] = a[0];
int spot = 0;
for(int i = 0; i < a.length; i++){
if(i != a.length-1 && a[i] != a[i+1]){
nums[spot] = a[i+1];
}
}
//figure out quantity of each number.
int[] quantities = new int[diffNums];
int spot2 = 0;
int spotcur = 0;
for(int i = 0; i < diffNums; i++){
int quant = 0;
while(a[spotcur] == a[spot2]){
quant++;
spotcur++;
}
spot2 = spotcur;
quantities[i] = quant;
}
//add them together and return compressed array
int spotter = 0;
for(int i = 0; i < diffNums; i++){
compressed[spotter] = quantities[i];
spotter++;
compressed[spotter] = nums[i];
spotter++;
}
return compressed;
}
}
Does anyone know how i can fix this crappy code? i am stuck on it
I think this problem could be solved with a lot less code. You could use an outer/inner loop construct something like the following:
public static int[] compress(int[] a) {
List<Integer> encoded = new ArrayList<>();
for (int i=0; i<a.length; i++) {
int num = a[i];
int count = 1;
for (int j=i+1; j<a.length; j++) {
int nextNum = a[j];
if (nextNum != num)
break;
count++;
i++;
}
encoded.add(count);
encoded.add(num);
}
return encoded.stream().mapToInt(i->i).toArray();
}
Also, the Arrays class contains a useful toString method already defined.
System.out.println(Arrays.toString(compress(potato)));
I need to find all the permutations for a given n(user input) without backtracking.
What i tried is:
import java.util.Scanner;
import java.util.Vector;
class Main {
private static int n;
private static Vector<Vector<Integer>> permutations = new Vector<>();
private static void get_n() {
Scanner user = new Scanner(System.in);
System.out.print("n = ");
n = user.nextInt();
}
private static void display(Vector<Vector<Integer>> permutations) {
for (int i = 0; i < factorial(n) - 1; ++i) {
for (int j = 0; j < n; ++j) {
System.out.print(permutations.elementAt(i).elementAt(j) + " ");
}
System.out.println();
}
}
private static int factorial(int n) {
int result = 1;
for (int i = 1; i <= n; ++i) {
result *= i;
}
return result;
}
private static int max(Vector<Integer> permutation) {
int max = permutation.elementAt(0);
for (int i = 1; i < permutation.size(); ++i)
if (permutation.elementAt(i) > max)
max = permutation.elementAt(i);
return max;
}
// CHECKS FOR ELEMENT COUNT AND 0 - (n-1) APPARITION
public static int validate_permutation(Vector<Integer> permutation) {
// GOOD NUMBER OF ELEMENTS
if (max(permutation) != permutation.size() - 1)
return 0;
// PROPER ELEMENTS APPEAR
for (int i = 0; i < permutation.size(); ++i)
if (!permutation.contains(i))
return 0;
return 1;
}
private static Vector<Integer> next_permutation(Vector<Integer> permutation) {
int i;
do {
i = 1;
// INCREMENT LAST ELEMENT
permutation.set(permutation.size() - i, permutation.elementAt(permutation.size() - i) + 1);
// IN A P(n-1) PERMUTATION FOUND n. "OVERFLOW"
while (permutation.elementAt(permutation.size() - i) == permutation.size()) {
// RESET CURRENT POSITION
permutation.set(permutation.size() - i, 0);
// INCREMENT THE NEXT ONE
++i;
permutation.set(permutation.size() - i, permutation.elementAt(permutation.size() - i) + 1);
}
} while (validate_permutation(permutation) == 0);
// OUTPUT
System.out.print("output of next_permutation:\t\t");
for (int j = 0; j < permutation.size(); ++j)
System.out.print(permutation.elementAt(j) + " ");
System.out.println();
return permutation;
}
private static Vector<Vector<Integer>> permutations_of(int n) {
Vector<Vector<Integer>> permutations = new Vector<>();
// INITIALIZE PERMUTATION SET WITH 0
for (int i = 0; i < factorial(n); ++i) {
permutations.addElement(new Vector<>());
for(int j = 0; j < n; ++j)
permutations.elementAt(i).addElement(0);
}
for (int i = 0; i < n; ++i)
permutations.elementAt(0).set(i, i);
for (int i = 1; i < factorial(n); ++i) {
// ADD THE NEXT PERMUTATION TO THE SET
permutations.setElementAt(next_permutation(permutations.elementAt(i - 1)), i);
System.out.print("values set by permutations_of:\t");
for (int j = 0; j < permutations.elementAt(i).size(); ++j)
System.out.print(permutations.elementAt(i).elementAt(j) + " ");
System.out.println("\n");
}
System.out.print("\nFinal output of permutations_of:\n\n");
display(permutations);
return permutations;
}
public static void main(String[] args) {
get_n();
permutations.addAll(permutations_of(n));
}
}
Now, the problem is obvious when running the code. next_permutation outputs the correct permutations when called, the values are set correctly to the corresponding the vector of permutations, but the end result is a mass copy of the last permutation, which leads me to believe that every time a new permutation is outputted by next_permutation and set into the permutations vector, somehow that permutation is also copied over all of the other permutations. And I can't figure out why for the life of me.
I tried both set, setElementAt, and an implementation where I don't initialize the permutations vector fist, but add the permutations as they are outputted by next_permutation with add() and I hit the exact same problem. Is there some weird way in which Java handles memory? Or what would be the cause of this?
Thank you in advance!
permutations.setElementAt(next_permutation(permutations.elementAt(i - 1)), i);
This is literally setting the vector at permutations(i) to be the same object as permutations[i-1]. Not the same value - the exact same object. I think this the source of your problems. You instead need to copy the values in the vector.
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.
I have to make a 3 way merge sort of an array. the array length is a in a power of 3, i.e. 3,9,27 etc. So I can use only one split function and not "left","mid","right".
Would like to get an answer how to repair it and why does not it work.
I have written the code, however don't know how to get it to work.
Here it is:
EDITED THE CODE, STILL DOES NOT WORK
public class Ex3 {
public static void main(String[] args) { //main function
Scanner in = new Scanner(System.in); //scanner
int size = in.nextInt();
int[] arr = new int[size];
for (int i = 0; i<arr.length; i++){
arr[i] = in.nextInt();
}
in.close();
arr = merge3sort (arr); //send to the function to merge
for (int i = 0; i<arr.length; i++){ //printer
System.out.print(arr[i]+ " ");
}
}
static int[] split(int[] m, int thirdNum) { //split function that splits to 3 arrays
int third[] = new int[m.length/3];
int third1[]=new int[m.length/3];
int third2[]=new int[m.length/3];
for(int i = 0; i<=m.length/3; i++)
third[i]=m[i];
for(int i=0; i<=m.length/3;i++)
third1[i]=m[i+thirdNum];
for(int i=0; i<=m.length/3;i++)
third2[i]=m[i+2*thirdNum];
return merge(third,third1,third2);
//return null;
}
static int minOf3(int[] a3) { //function that finds out how what is the index of the smallest number
int num0 = a3[0];
int num1 = a3[1];
int num2 = a3[2];
int idx = 0;
if(num0<num1 && num1<num2)
idx=0;
if(num1<num0 && num0<num2)
idx=1;
else
idx=2;
return idx;
}
static int[] merge(int[] th0, int[] th1, int[] th2) { //function that sorts the numbers between 3 arrays
int len0=th0.length;
int len1=th1.length;
int len2=th2.length;
int[] united = new int[len0+len1+len2];
int ind = 0; int i0=0; int i1=0; int i2=0;
while(i0<len0 && i1<len1 && i2<len2){
if(th0[i0]<th1[i1]){
if(th0[i0]<th2[i2]){
united[ind]=th0[i0];
i0=i0+1;
}//end inner if
else{
united[ind]=th2[i2];
i2=i2+1;
}//end inner else
}//end outer if
else{
united[ind]=th1[i1];
i1=i1+1;
}//end outer else
ind=ind+1;
}//end while
for (int i = i0; i < len0; i = i + 1) {
united[ind] = th0[i];
ind = ind + 1;
}
for (int i = i1; i < len1; i = i + 1) {
united[ind] = th1[i];
ind = ind + 1;
}for (int i = i2; i < len2; i = i + 1) {
united[ind] = th2[i];
ind = ind + 1;
}
return united;
}
static int[] merge3sort(int[] m) { //function that glues all together
if (m.length == 1) {
return m;
}
else{
return merge(merge3sort(split(m,m.length/3)),merge3sort(split(m,m.length/3)),merge3sort(split(m,m.length/3))); }
}
I get the following exception:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at ololosh1.Ex3.split(Ex3.java:27)
at ololosh1.Ex3.merge3sort(Ex3.java:98)
at ololosh1.Ex3.main(Ex3.java:15)
Look at this part of your code:
for(int i = 0; i<=m.length/3; i++)
third[i]=m[i];
for(int i=0; i<=m.length/3;i++)
third1[i]=m[i+thirdNum];
for(int i=0; i<=m.length/3;i++)
third2[i]=m[i+2*thirdNum];
Arrays are indexed from 0 to length-1. Each third* array has length m.length/3. Therefore their index can only go up to m.length/3 - 1. Yet you are indexing up to and including m.length/3.
Once you get your application working correctly, you really should clean it up. There is a lot of redundancy. For example, you are using the expression m.length/3 multiple times in method split() but you are also passing that same value to it as an argument.
public class AssignmentChapter8
{
public static void main(String[] args)
{
int randomNumbers = new int[100];
int counter = 0;
while(counter < randomNumbers.length)
{
randomNumbers[counter] = (int)(Math.random() * 25);
counter++;
}
int oddNumbers[] = new int[100];
oddNumbers[] = getOddNumbers(randomNumbers);
int evenNumbers[] = new int[100];
evenNumbers[] = getEvenNumbers(randomNumbers);
System.out.println("The odd numbers are:");
for(int k = 0; k < oddNumbers.length; k++)
System.out.print("\t" + oddNumbers[k]);
System.out.println("The even numbers are:");
for(int l = 0; l < evenNumbers.length; l++)
System.out.print("\t" + evenNumbers[l]);
}
public static int getOddNumbers(int randomNumbers)
{
int oddNumbers[] = new int[100];
int counterA = 0;
int counterB = 0;
int counter = 0;
int placeholder;
while(counter < randomNumbers.length)
{
if(randomNumbers[counterA] % 2 > 0)
{
oddNumbers[counterB] = randomNumbers[counterA];
counterB++;
}
counterA++;
counter++;
}
return oddNumbers;
}
public static int getEvenNumbers(int randomNumbers)
{
int evenNumbers[] = new int[100];
int counterA = 0;
int counterB = 0;
int counter = 0;
int placeholder;
while(counter < randomNumbers.length)
{
if(randomNumbers[counterA] % 2 > 0)
{
evenNumbers[counterB] = randomNumbers[counterA];
counterB++;
}
counterA++;
counter++;
}
return evenNumbers;
}
}
I have been trying to execute a program to sort variables in arrays, but I keep getting a ';' expected error in the line after declaration of the array where the program is supposed to retrieve an array from a function. Any help would be appreciated.
This is bad syntax (which causes the ';' expected error ):
oddNumbers[] = getOddNumbers(randomNumbers);
The brackets are not needed. You can do this:
oddNumbers = getOddNumbers(randomNumbers);
Besides that, you have plenty of errors:
int randomNumbers[] = new int[100]; // you need the brackets
Your return value in the method declaration is wrong (you are returning an array, not an int):
public static int[] getEvenNumbers(int randomNumbers)
int oddNumbers[] = new int[100];
By initializing oddNumbers become an array. when you want to assign values,
oddNumbers={elements of array}
Both left and right hand side both should arrays.
May be you should use IDE for coding then it may help you to understand some issues like this.