When population oddList, evenList and negativeList from the inputList the program only populates it with one int instead of all corresponding ints from the inputList array. The output should be a list from each array whose numbers correspond to its title. The numbers are input by user into inputList array and then from there it determines whether it is odd, even, and negative and then fills the corresponding arrays.
I.E. evenList is filled with even ints from inputList.
public class ProjectTenOne
{
public static void main(String[] args)
{
int[] inputList = new int[10];
int[] oddList = null;
int[] evenList = null;
int[] negativeList = null;
int evenCount = 0;
int oddCount = 0;
int negCount = 0;
Scanner input = new Scanner(System.in);
//System.out.println("Enter any ten integers: ");
for(int list = 0; list < inputList.length; list++)
{
System.out.println("Enter any " + (inputList.length - list) + " integers: ");
inputList[list] = input.nextInt();
}
System.out.println();
System.out.println("The numbers you entered: ");
for(int in = 0; in < inputList.length; in++)
{
System.out.println(inputList[in]);
}
for(int ls = 0; ls< inputList.length; ls++)
{
if(inputList[ls] % 2 == 0)
{
evenCount = evenCount +1;
}
if(inputList[ls] % 2 != 0)
{
oddCount = oddCount +1;
}
if(inputList[ls] < 0)
{
negCount = negCount +1;
}
}
evenList = new int[evenCount];
oddList = new int[oddCount];
negativeList = new int[negCount];
for(int l = 0; l < inputList.length; l++)
{
if((inputList[l] % 2) == 0)
{
for(int j = 0; j < evenList.length; j++)
{
evenList[j] = inputList[l];
}
}
if((inputList[l] % 2) != 0)
{
for(int k = 0; k < oddList.length; k++)
{
oddList[k] = inputList[l];
}
}
if(inputList[l] < 0)
{
for(int h = 0; h < negativeList.length; h++)
{
negativeList[h] = inputList[l];
}
}
}
System.out.println("The ODD List is: ");
for(int i = 0; i < oddList.length; i++)
{
System.out.println(oddList[i]);
}
System.out.println("The EVEN List is: ");
for(int j = 0; j < evenList.length; j++)
{
System.out.println(evenList[j]);
}
System.out.println("The NEGATIVE List is: ");
for(int k = 0; k < oddList.length; k++)
{
System.out.println(negativeList[k]);
}
}
}
I'll take evenList as the example here, but the same applies to the other two arrays as well.
In your code, you iterate over your inputList and check for an even number. If it is even, you set the entire evenList array to the found value, instead of just a single element.
You can solve this problem by declaring an int outside of your outer loop that keeps track of the number of even numbers entered. As an example:
int evenIndex = 0;
for(int l = 0; l < inputList.length; l++)
{
if((inputList[l] % 2) == 0)
{
evenList[evenIndex++] = inputList[l];
}
/*Other code*/
}
You also made a mistake in your last loop. You iterate over negativeList, but you use the size of evenList. This will result in an ArrayIndexOutOfBoundsException when negativeList is smaller than evenList.
Related
Trying to write a program that asks the a user for 10 integers as input. The program
places the even integers into an array called evenList, the odd integers into
an array called oddList, and the negative numbers into an array called
negativeList. The program displays the contents of the three arrays after
all of the integers have been entered.
This is my code:
import java.util.Scanner;
public class Main
{
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int countNeg = 0;
int countOdd = 0;
int countEven = 0;
int[] list = new int[10];
System.out.println("Please enter 10 integers:");
for(int i = 0; i < list.length; i++)
{
list[i] = scan.nextInt();
if(list[i] < 0)
{
countNeg++;
}
if(list[i] % 2 == 0 && list[i] > 0)
{
countEven++;
}
if(list[i] % 2 == 1 && list[i] > 0)
{
countOdd++;
}
}
int[] oddList = new int[countOdd];
int[] evenList = new int[countEven];
int[] negativeList = new int[countNeg];
for(int i = 0; i < list.length; i++)
{
if(list[i] < 0)
{
for(int j = 0; j < countNeg; j++)
{
negativeList[j] = list[i];
}
}
}
for(int i = 0; i < list.length; i++)
{
if(list[i] % 2 == 0 && list[i] > 0)
{
for(int j = 0; j < countEven; j++)
{
evenList[j] = list[i];
}
}
}
for(int i = 0; i < list.length; i++)
{
if(list[i] % 2 == 1 && list[i] > 0)
{
for(int j = 0; j < countOdd; j++)
{
oddList[j] = list[i];
}
}
}
for (int i : negativeList)
{
System.out.print(i + " ");
}
System.out.println();
for (int i : evenList)
{
System.out.print(i + " ");
}
System.out.println();
for (int i : oddList)
{
System.out.print(i + " ");
}
}
}
The program prints the Arrays with the correct amount of values but the wrong numbers. It prints only the last negative, even, or odd number to be input. ex input is 1, 2, 3, 4, 5, 6, -1, -2, -3, -4. For negativeList it prints -4 -4 -4 -4. Im guessing something is wrong in the loops after the arrays are created. Please help!!
you can very much simplify your code with using ArrayList instead of array. For example:
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int length = 10;
System.out.println("Please enter 10 integers:");
List<Integer> oddList = new ArrayList<>();
List<Integer> evenList = new ArrayList<>();
List<Integer> negativeList = new ArrayList<>();
for (int i = 0; i < length; i++) {
int n = scan.nextInt();
if (n < 0) {
negativeList.add(n);
} else if (n % 2 == 0) {
evenList.add(n);
} else {
oddList.add(n);
}
}
for (int i : negativeList) {
System.out.print(i + " ");
}
System.out.println();
for (int i : evenList) {
System.out.print(i + " ");
}
System.out.println();
for (int i : oddList) {
System.out.print(i + " ");
}
}
there are a few issues with the code you provided.
First, in the for loops that initialize the negativeList, evenList, and oddList arrays, you are overwriting the values at each iteration. This means that the final arrays will only contain the last value that was assigned to them. To fix this, you can use a counter variable to keep track of the next index to be filled in each array, like this:
int negCounter = 0;
int evenCounter = 0;
int oddCounter = 0;
for(int i = 0; i < list.length; i++)
{
if(list[i] < 0)
{
negativeList[negCounter] = list[i];
negCounter++;
}
}
for(int i = 0; i < list.length; i++)
{
if(list[i] % 2 == 0 && list[i] > 0)
{
evenList[evenCounter] = list[i];
evenCounter++;
}
}
for(int i = 0; i < list.length; i++)
{
if(list[i] % 2 == 1 && list[i] > 0)
{
oddList[oddCounter] = list[i];
oddCounter++;
}
}
Second, you are not checking if the input values are integers. If the user enters a non-integer value, the program will throw an exception. You can add a check to make sure that the input is an integer like this:
if(scan.hasNextInt())
{
list[i] = scan.nextInt();
// ... rest of the code
}
else
{
System.out.println("Please enter an integer.");
// If the input is not an integer, discard it and move to the next
input
scan.next();
}
I am taking 10 elements and performing a bubble sort on them. I want to add an algorithm that repeats the sort until no swaps are needed to make this more efficient.
Essentially I want to:
repeat until no swaps done in a pass
For elements 1 to (n-1)
compare contents of element value 1 with the contents of the next value
if value 1 is greater than value 2
then swap the values
This is what I have done so far :
{
//create array
int[] iList = new int[10];
Scanner sc = new Scanner(System.in);
//takes in array input for 10 numbers
System.out.println("Enter a array of numbers ");
for(int i = 0; i< 10; i++ )
{
int num = i + 1;
System.out.println("Enter number " + num);
iList[i] = sc.nextInt();
}
//Bubble sorts the array
System.out.println("The array =");
for(int a = 0; a < iList.length; a++ )
{
for(int b = a+1; b < iList.length; b++)
{
if(iList[a] > iList[b])
{
int iTemp = iList[a];
iList[a] = iList[b];
iList[b] = iTemp;
}
System.out.println("Progress = " + Arrays.toString(iList) );
}
}
} ```
Here is my implementation :
public static void sort(int[] nums) {
boolean isSwapped;
int size = nums.length - 1;
for (int i = 0; i < size; i++) {
isSwapped = false;
for (int j = 0; j < size - i; j++) {
if (nums[j] > nums[j+1]) {
int temp = nums[j];
nums[j] = nums[j + 1];
nums[j + 1] = temp;
isSwapped = true;
}
}
if (!isSwapped) break;
}
System.out.println("Sorted Array: " + Arrays.toString(nums));
}
I have written a program in ArrayList to find the sorted array. But I have to find the sum of the numbers entered as well.
I couldn't succeed in getting the results as it is in the array list
import java.util.ArrayList;
import java.util.Scanner;
public class project1 {
public static void main(String[] args) {
int add = 0;
Scanner input = new Scanner(System.in);
System.out.print("Enter 5 numbers: ");
ArrayList<Integer> list = new ArrayList<>();
for (int i = 0; i < 5; i++) list.add(input.nextInt());
System.out.println("add" +add);
System.out.println("Sorting numbers...");
sort(list);
System.out.println("Displaying numbers...");
System.out.println(list);
}
public static void sort(ArrayList<Integer> list) {
for (int i = 0; i < list.size() - 1; i++) {
int currentMin = list.get(i);
int currentIndex = i;
for (int j = i + 1; j < list.size(); j++) {
if (currentMin > list.get(j)) {
currentMin = list.get(j);
currentIndex = j;
}
}
if (currentIndex != i) {
list.set(currentIndex, list.get(i));
list.set(i, currentMin);
}
}
}
}
I am looking to get the sum of the entered numbers along with sorting. Any help will be very appreciated.
change this
for (int i = 0; i < 5; i++) list.add(input.nextInt());
to this
int sum = 0;
for (int i = 0; i < 5; i++){
int num = input.nextInt();
list.add(num);
sum += num;
}
the value of the sum is saved inside sum and you can do what ever you want with it.
I am using the For loop to add the values the user entered to a var name sum that is located out side of the for loop and when the for loop is done you have the sum
You could just write sum += currentMin at the bottom of the for (int i; ... loop. This way you count every number exactly once, after it is put in its final place.
ArrayList<Integer> list = new ArrayList<>();
int sum = 0
for (int i = 0; i < 5; i++) {
int in = input.nextInt();
sum = sum + in;
list.add(in);
}
I am getting user input for function (smallest or largest) and for populating array. Then according to the input function i want to compare consecutive elements and find the smallest or largest number. I cannot understand why and how to fix my code.
The code runs but does not work as supposed to. The smallest and largest numbers are all wrong
import java.util.Scanner;
public class App {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Are you trying to find the Smallest or Largest number in an array of numbers? S/L");
String functionExpected = sc.nextLine();
System.out.println("How many elements you plan to enter? ");
int lengthOfArray = sc.nextInt();
// Populating array according to input and length
int[] numbersArray = new int[lengthOfArray];
for (int i = 0; i < numbersArray.length; i++) {
System.out.println("Enter an element here: ");
numbersArray[i] = sc.nextInt();
}
// Print out array
for (int i = 0; i < numbersArray.length; i++) {
System.out.print(numbersArray[i] + " ");
}
System.out.println();
if (functionExpected.equalsIgnoreCase("L")) {
int temp = 0;
System.out.println("We are going to find the largest number in the array of elements you enter!");
for (int i = 0; i < numbersArray.length; i++) {
for (int j = 1; j < numbersArray.length;) {
if (numbersArray[i] > numbersArray[j]) {
temp = numbersArray[i];
break;
} else {
temp = numbersArray[j];
break;
}
}
}
System.out.println("Largest of the three numbers is : " + temp);
}
if (functionExpected.equalsIgnoreCase("S")) {
int temp = 0;
System.out.println("We are going to find the smallest number in the array of elements you enter!");
for (int i = 0; i < numbersArray.length; i++) {
for (int j = 1; j < numbersArray.length;) {
if (numbersArray[i] > numbersArray[j]) {
temp = numbersArray[j];
break;
} else {
temp = numbersArray[i];
break;
}
}
}
System.out.println("Smallest of the three numbers is : " + temp);
}
}
}
As pointed out by the comments the inner loops (j based) are completely unnecessary.
int temp = numbersArray[0];
for (int i = 1; i < numbersArray.length; i++) {
if(numbersArray[i] > temp) {
temp = numbersArray[i]
}
}
Just switch the > to < in the if for smallest/largest.
I asked a question on helping me with this question about a week ago
Java permutations
, with a problem in the print permutation method. I have tidied up my code and have a working example that now works although if 5 is in the 5th position in the array it doesn't print it. Any help would be really appreciated.
package permutation;
public class Permutation {
static int DEFAULT = 100;
public static void main(String[] args) {
int n = DEFAULT;
if (args.length > 0)
n = Integer.parseInt(args[0]);
int[] OA = new int[n];
for (int i = 0; i < n; i++)
OA[i] = i + 1;
System.out.println("The original array is:");
for (int i = 0; i < OA.length; i++)
System.out.print(OA[i] + " ");
System.out.println();
System.out.println("A permutation of the original array is:");
OA = generateRandomPermutation(n);
printArray(OA);
printPermutation(OA);
}
static int[] generateRandomPermutation(int n)// (a)
{
int[] A = new int[n];
for (int i = 0; i < n; i++)
A[i] = i + 1;
for (int i = 0; i < n; i++) {
int r = (int) (Math.random() * (n));
int swap = A[r];
A[r] = A[i];
A[i] = swap;
}
return A;
}
static void printArray(int A[]) {
for (int i = 0; i < A.length; i++)
System.out.print(A[i] + " ");
System.out.println();
}
static void printPermutation(int[] p)
{
int n = p.length-1;
int j = 0;
int m;
int f = 0;
System.out.print("(");
while (f < n) {
m = p[j];
if (m == 0) {
do
f++;
while (p[f] == 0 && f < n);
j = f;
if (f != n)
System.out.print(")(");
}
else {
System.out.print(" " + m);
p[j] = 0;
j = m - 1;
}
}
System.out.print(" )");
}
}
I'm not too crazy about
int n = p.length-1;
followed by
while (f < n) {
So if p is 5 units long, and f starts at 0, then the loop will be from 0 to 3. That would seem to exclude the last element in the array.
You can use the shuffle method of the Collections class
Integer[] arr = new Integer[] { 1, 2, 3, 4, 5 };
List<Integer> arrList = Arrays.asList(arr);
Collections.shuffle(arrList);
System.out.println(arrList);
I don't think swapping each element with a random other element will give a uniform distribution of permutations. Better to select uniformly from the remaining values:
Random rand = new Random();
ArrayList<Integer> remainingValues = new ArrayList<Integer>(n);
for(int i = 0; i < n; i++)
remainingValues.add(i);
for(int i = 0; i < n; i++) {
int next = rand.nextInt(remainingValues.size());
result[i] = remainingValues.remove(next);
}
Note that if order of running-time is a concern, using an ArrayList in this capacity is n-squared time. There are data-structures which could handle this task in n log n time but they are very non-trivial.
This does not answer the problem you have identified.
Rather i think it identifies a mistake with your generateRandomPermutation(int n) proc.
If you add a print out of the random numbers generated (as i did below) and run the proc a few times it allows us to check if all the elements in the ARRAY TO BE permed are being randomly selected.
static int[] generateRandomPermutation(int n)
{
int[] A = new int[n];
for (int i = 0; i < n; i++)
A[i] = i + 1;
System.out.println("random nums generated are: ");
for (int i = 0; i < n; i++) {
int r = (int) (Math.random() * (n));
System.out.print(r + " ");
Run the proc several times.
Do you see what i see?
Jerry.