I am trying to find palindrome no but every time it is showing false for every no even for 121
please Help....
public boolean isPalindrome(int x) {
if(x<0 || x%10==0){
return false;
}
int rev = 0;
while(x!=0){
rev=(rev*10)+(x%10);
x/=10;
}
if(x==rev){
return true;
}
else{
return false;
}
}
enter image description here
As an option, you may create something like this:
public boolean isPalindrome(int x) {
StringBuilder sb = new StringBuilder();
sb.append(x);
return sb.toString().equals(sb.reverse().toString());
}
Because after your while loop ends, x will be 0, you have to act on a copy instead
public boolean isPalindrome(int x) {
int num = x;
if(x<0 || x%10==0){
return false;
}
int rev = 0;
while(x!=0){
rev=(rev*10)+(x%10);
x/=10;
}
if(num==rev){
return true;
}
else{
return false;
}
}
All you need to do is build the new number as you reduce the original. Then compare the two.
for (int i : new int[]{121,12321, 123,34543,20012}) {
System.out.printf("%6d - %s%n", i, isPalindrome(i));
}
public static boolean isPalindrome(int numb) {
int n = 0;
for (int b = numb; b > 0;) {
n *= 10;
n += b%10;
b/=10;
}
return n == numb;
}
Prints
121 - true
12321 - true
123 - false
34543 - true
20012 - false
Hope this is useful:
public static boolean palindrome(int n) {
int nPalindrome = 0;
int nCopy = n;
while (n != 0) {
nPalindrome = nPalindrome *10 + n % 10;
n = n / 10;
}
if (nCopy == nPalindrom) {
return true;
} else {
return false;
}
}
You function can be as simple as below
public static void main(String args[]){
int r,sum=0;
int n=454;//It is the number variable to be checked for palindrome
if(isPalindrome(n)) {
System.out.println("palindrome number ");
} else {
System.out.println("not palindrome number ");
}
}
public boolean isPalindrome(int n) {
while(n>0){
r=n%10; //getting remainder
sum=(sum*10)+r;
n=n/10;
}
return n==sum;
}
Related
a super silly question but why does the method prime recurse infinitely ?
this is a simple java code where i'm trying to make a method i can call to get the prime of parameter x , but it tells me that the method will recurse infinitely , i tried copy pasting the code of the prime method to the main method and it worked well , so can someone help please?
`
import java.util.*;
public class Mavenproject2 {
static int prime(int x) {
boolean f = true;
if (x == 1 || x == 0) {
f = false;
} else {
for (int i = 2; i < x; i++) {
if (x % i == 0) {
f = false;
break;
}
}
}
if (f) {
System.out.println("prime");
} else {
System.out.println("not prime");
}
return prime(x);
}
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("enter number");
int x = input.nextInt();
System.out.println(prime(x));
}
}
`
If you just want to know if the number passed in is prime. You need to change your return type to a bool and return f.
You're returning prime(x) which will keep calling into itself.
I would actually do something like this
import java.util.*;
public class Mavenproject2 {
static string prime(int x) {
boolean f = true;
if (x == 1 || x == 0) {
f = false;
} else {
for (int i = 2; i < x; i++) {
if (x % i == 0) {
f = false;
break;
}
}
}
if (f) {
return "prime";
}
return "not prime";
}
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("enter number");
int x = input.nextInt();
System.out.println(prime(x));
}
}
I would like to apologise in advance if im doing something wrong with the code formatting because this is my second time posting here
I have a java assignment due in a couple of days in which the user enters a string and only the integers are collected from it and placed in the array intArray
Now i think i got the logic right in the code below but when i run it in the main, it asks for the string and the boolean, when i enter both it gives me the error
"Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 115"
This is what i entered for example
"Enter a string and true if you want to skip errors or false if you want to skip errors
sdak23
false"
this is my main:
import java.util.Scanner;
public class MainStringToIntArray {
public static void main(String[] args) {
Scanner intut = new Scanner(System.in);
Scanner input = new Scanner(System.in);
StringToIntArray s1 = new StringToIntArray();
System.out.println("Enter a string and true if you want to skip errors or false if you want to skip errors");
s1.scanStringToIntArray(intut.next(), input.nextBoolean());
}
}
import java.util.Arrays;
import java.util.Scanner;
public class StringToIntArray {
private int[] intArray = new int[10];
public StringToIntArray() {
Arrays.fill(intArray, Integer.MIN_VALUE);
}
public int indexOf(int intToFind) {
int b = 0;
for (int a = 0; a < intArray.length; a++) {
if (intArray[a] == intToFind) {
b = intArray[a];
}
else {
b = -1;
}
}
return b;
}
public int indexOf(String intToFind) {
int b = 0;
for (int a = 0; a < intArray.length; a++) {
if (intArray[a] == Integer.parseInt(intToFind)) {
b = intArray[a];
}
else {
b = -1;
}
}
return b;
}
public boolean contains(int intToFind) {
int a = indexOf(intToFind);
if (a > 0) {
return true;
}
else {
return false;
}
}
public boolean contains(String intToFind) {
int a = indexOf(intToFind);
if (a > 0) {
return true;
}
else {
return false;
}
}
public int get(int index) {
if(index < 0 && index > 10) {
return Integer.MIN_VALUE;
}
else {
return intArray[index];
}
}
public boolean scanStringToIntArray(String s, Boolean skipErrors) {
Boolean result = null;
Scanner input = new Scanner(s);
int l = s.length();
if ((skipErrors)) {
String discard = null;
for (int a = 0; a < l; a++) {
for (int z = 0; z < l; z++) {
if (input.hasNextInt(s.charAt(z))) {
intArray[a] = s.charAt(z);
System.out.println(a);
result = true;
}
else {
discard = discard + s.charAt(z);
}
}
}
}
else {
for (int v = 0; v < l; v++) {
for (int p = 0; p < l; p++) {
if ((input.hasNextInt(s.charAt(p)))) {
intArray[v] = s.charAt(p);
System.out.println(v);
}
else {
System.out.println(v);
result = false;
}
}
}
}
return result;
}
}
The issue is in the get method. It is logically impossible for the index to be both less than 0 and greater than 10; you probably want to use the logical or operator (||). Also, the maximum index of the array is actually 9, as arrays are zero indexed.
public int get(int index) {
if(index < 0 || index > 9) {
return Integer.MIN_VALUE;
}
else {
return intArray[index];
}
}
There are other logical errors in your code as well. All your indexOf methods should be returning the index where the element was first found instead of the element itself and your else branch is always resetting it to -1 each time it is not found.
So I have a program that will find the prime factorization of a number.
public static void primeFactors(int number){
int i=2;
while(number>1){
if (number%i==0){
System.out.println(i);
number/=i ;
}else{
i++;
if(isPrime(i)==true){
System.out.println(i);
number/=i;
}else{
i++;
}}}}
But the thing is I want it to return as an Array. And It has to be able to take a large number and run within 5 seconds. So I converted the working algorithm to this:
public static int[] primeFactors2(int number){
int[] arrayINT =new int[10];
int i = 2;
int index=0;
while(i<=number/2){
if(number %i==0 && isPrime(i)){
arrayINT[index]=i;
index++;
}
i++;
}
return arrayINT;
}}
And this doesn't return the right result, and isn't efficient speed wise. What the heck am I doing wrong!
And here is isPrime():
public static boolean isPrime(int number){
if (number<2){
return false;
}
if (number==2){
return true;
}
if (number%2==0){
return false;
}
int ceiling=number;
for(int i=3;number>i&&ceiling>i;i+=2){
if(number%i==0){
return false;
}
ceiling=number/i;
} return true;
}
I have modified the code a bit to accommodate your requirement. Please take a look.
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
--
public static void main(String[] args) {
primeFactors(630);
System.out.println(Arrays.toString(primeFactors2(630)));
}
public static void primeFactors(int number) {
int i = 2;
int init = number;
while(i<=init/2){
if(number %i==0 && isPrime(i)){
System.out.println(i);
number/=i;
i--;
}
i++;
}
}
public static Integer[] primeFactors2(int number) {
List<Integer> list = new ArrayList<>();
int i = 2;
int init = number;
while(i<=init/2){
if(number %i==0 && isPrime(i)){
list.add(i);
number/=i;
i--;
}
i++;
}
return list.toArray(new Integer[list.size()]);
}
public static boolean isPrime(int number) {
if (number < 2) {
return false;
}
if (number == 2) {
return true;
}
if (number % 2 == 0) {
return false;
}
int ceiling = number;
for (int i = 3; number > i && ceiling > i; i += 2) {
if (number % i == 0) {
return false;
}
ceiling = number / i;
}
return true;
}
As far big numbers are concerned, i know there is a class available in java BigInteger, but i have a constraint that i can't use this and i have to perform division without using library.
This is what i have tried so far, but got memory leakage issues and not getting any answer
private Integer getDivisionResult(ArrayList<Integer> first, ArrayList<Integer> second) {
int firstLength = first.size();
int secondLength = second.size();
int counter = 0;
if (firstLength < secondLength) {
return counter;
}
do {
int carry = 0, cursor1 = firstLength - 1, cursor2 = secondLength - 1;
for (int i = firstLength - 1; i >= 0; i--, cursor1--, secondLength--) {
int value = 0, from = 0;
from = first.get(cursor1) - carry;
if (from < (cursor2 < 0 ? 0 : second.get(cursor2))) {
if (cursor1 > 0) {
from = 10 + from;
}
carry = 1;
} else {
carry = 0;
}
value = from - (cursor2 < 0 ? 0 : second.get(cursor2));
first.set(i, value);
}
counter++;
}while (isLesserThan(second,first));
return counter;
}
private boolean isLesserThan(ArrayList<Integer> list, ArrayList<Integer> firstList) {
boolean result = true;
if (list.size() < firstList.size()) {
return true;
}
for (int i = 0; i < list.size(); i++) {
if (firstList.get(i) > list.get(i)) {
result = true;
break;
} else if (firstList.get(i) == list.get(i)) {
continue;
} else {
result = false;
break;
}
}
return result;
}
I'm calling getDivisionResult inside this method, after passing certain error cases:
/**
* #param numOne
* #param numTwo
* #return sign : true (negative) , false (positive)
*/
public Result getResult(String numOne, String numTwo) {
Result result = new Result();
int res = 0;
boolean sign = false;
ArrayList<Integer> firstNum;
ArrayList<Integer> secondNum;
if (isNegative(numOne)) {
firstNum = getArray(numOne.substring(1));
if (isNegative(numTwo)) {
sign = false;
secondNum = getArray(numTwo.substring(1));
} else {
secondNum = getArray(numTwo);
sign = true;
}
} else {
firstNum = getArray(numOne);
if (isNegative(numTwo)) {
sign = true;
secondNum = getArray(numTwo.substring(1));
} else {
secondNum = getArray(numTwo);
}
}
if (isNull(secondNum)) {
result.setSign("Division by 0 is not permissable");
result.setValue(res);
return result;
} else {
if (isNull(firstNum)) {
result.setSign("");
result.setValue(res);
return result;
}
firstNum = getNumberWithoutZeroes(firstNum);
secondNum = getNumberWithoutZeroes(secondNum);
res = getDivisionResult(firstNum, secondNum);
if (sign) {
result.setSign("-");
} else {
result.setSign("");
}
result.setValue(res);
}
return result;
}
private ArrayList<Integer> getNumberWithoutZeroes(ArrayList<Integer> num) {
ArrayList<Integer> list = new ArrayList<>();
for (Integer x : num) {
if (x == 0) {
continue;
} else {
list.add(x);
}
}
return list;
}
private boolean isNegative(String num) {
boolean result = false;
if (num.startsWith("-")) {
result = true;
}
return result;
}
private boolean isNull(ArrayList<Integer> num) {
boolean result = true;
for (Integer x : num) {
if (x > 0) {
result = false;
}
}
return result;
}
private ArrayList<Integer> getArray(String num) {
ArrayList<Integer> list = new ArrayList<>();
char[] arr = num.toCharArray();
for (int i = 0; i < num.length(); i++) {
list.add(Integer.valueOf(arr[i]));
}
return list;
}
if someone can help me to give a better solution to my problem, I would be grateful
I've made the solution to my own problem, but the problem now is its processing speed.
So in a few words i made a class extending the RandomGenerator to randomly giving back PRIME, POWER OF 2(2,4,8,16,32,64,128 etc) , FIBONACCI AND SQUARE NUMBERS (1,4,9,16,25,36 etc). Then i made a simple program to call my class and giving back random numbers while the user defines the space (1,n). Both programs compile just fine. My problem is that when i run the program it always returns 0 for each value. I'm new to java. Can anyone help me?
import acm.util.*;
public class RandomGeneratorImproved2 extends RandomGenerator
{
private int i,j,a,c,d,e,temp,n,Pnumber,Fnumber,number2,numbersq;
private long b;
boolean flag,flag2,flag3,flag4,flag5;
private double temp1;
public RandomGeneratorImproved2 (int n)
{
this.n = n;
}
public void nextPrime(int n) // PRIME NUMBERS
{
Pnumber = rgen.nextInt(1, n);
i=2;
flag2 = false;
if ( Pnumber == 1 ) // Check for value 1 cause it cannot check it inside the loop
{
flag2=true;
}
while ( (i<n) && (flag2 == false) )
{
flag = true;
j=2;
do
{
a = i%j;
if ( (a == 0) && (i != j) )
{
flag = false;
}
if (i!=j-1)
{
j = j+1;
}
} while ( j<i );
if ((flag == true) && (Pnumber==i)) //
{
flag2 = true;
}
if ((i==99) && (flag2==false)) // restart if the number is not prime
{
i = 1;
Pnumber = rgen.nextInt(1, n);
}
i = i + 1;
}
}
public int getPrime() //POWER OF 2 NUMBERS
{
return Pnumber;
}
public void nextPowerof2(int n)
{
number2 = rgen.nextInt(1, n);
i=1;
b=2;
flag3 = false;
while ( i<n ) // n <= 31
{
if (number2 == b)
{
flag3 = true;
}
b = 2*b;
if ((i == n-1) && (flag3==false))
{
i=1;
number2 = rgen.nextInt(1,n);
b=2;
}
i=i+1;
}
}
public int getPowerof2()
{
return number2;
}
public void nextFibonacciNumber(int n) // FIBONACCI NUMBERS
{
Fnumber = rgen.nextInt(1, n);
c=0;
d=1;
flag4 = false;
i=1;
while ( i<n && flag4==false )
{
temp = d;
d = d + c;
c = temp;
i=i+1;
if (Fnumber == d)
{
flag4 = true;
}
if ((flag4 == false) && (i==n))
{
i=1;
c=0;
d=1;
Fnumber = rgen.nextInt(1, n);
}
}
}
public int getFibonacciNumber()
{
return Fnumber;
}
public void setSquareNumber(int n) // SQUARE NUMBERS
{
numbersq = rgen.nextInt(1, n);
flag5 = false;
i=1;
temp1 = Math.sqrt(n);
while ( i<temp1 && flag5 == false )
{
e = i*i;
i = i + 1;
if ( numbersq == e )
{
flag5 = true;
}
if ( i == 20 && flag5 == false )
{
i=1;
numbersq = rgen.nextInt(1, n);
}
}
}
public int getSquareNumber()
{
return numbersq;
}
public String toString()
{
return "Your Prime number is : " + Pnumber + "\nYour Power of 2 number is : " + number2 + "\nYour Fibonacci number is : " + Fnumber + "\nYour square number is : " + numbersq;
}
private RandomGenerator rgen = RandomGenerator.getInstance();
}
import acm.program.*;
public class caller2 extends Program
{
public void run()
{
int n = readInt("Please give me an integer to define the space that i'll look for numbers : ");
RandomGeneratorImproved2 r1 = new RandomGeneratorImproved2(n);
println(r1);
}
}
As stated you've only defined those method. You never call any of the methods that are setting those values so all are still in their initialized state. Try adding the following to the constructor after setting n;
nextPrime(n);
nextFibonaccitNumber(n);
nextPowerof2(n);