Was doing some Java practices and I got stuck at this particular question, I am given the following code:
public class DistanceSeparator {
public static void main(String[] args) {
printSeparatorSequence(3);
printSeparatorSequence(5);
printSeparatorSequence(8);
}
public static void printSeparatorSequence(int numberOfElements) {
for () {
}
System.out.println();
} //end of method printSeparatorSequence
} // end of class
And I am supposed to modify the code using A SINGLE FOR LOOP to show that:
If numberOfElements = 5
1 3 7 13 21
If numberOfElements = 7
1 3 7 13 21 31 43
Each showing an increment of + 2, +4, +6, +8, +10 and +12
The final output is to be this:
1 3 7
1 3 7 13 21
1 3 7 13 21 31 43 57
I just can't seem to get my head around how to get that outcome, and this is after 2hours of trying (yes I am that bad). Any help, please?
edit This was what I had, before deciding to seek help, it's obviously not working.
int j = 0;
for (int i = 1; i <= numberOfElements; i++) {
j = i * 2; // + by how much
int z = i + j; //sum
System.out.print(z + "");
}
edit 2 now I get it, oh my, to think I was so close. Guess I was too cluttered after being stuck for some time. Thanks a ton!
Here is the code to accomplish result you expected.
int current = 1;
for(int i = 0; i < numberOfElements; i++) {
current += i*2;
System.out.print(current + " ");
}
You just need to keep another variable to keep track of the difference (the change), and then constantly update it by the power of 2 of the iteration, i.e. for the first loop only increase it by 2^1, then by 2^2, then 2^3 and so on).
An example of how to achieve that:
for (int i = 0, diff = 0; i < numberOfElements; i++, diff += 2*i) {
System.out.print((1 + diff) + " ");
}
UPDATE: After you've edited your question with your code segment, you can see your problem was with this line:
int z = i + j; //sum
Since both i and j advance with each iteration, you lose your offset (you constantly reset it). You need to keep it static (like in my example: 1), and only update j by 2*i each iteration, otherwise your "base" for calculation is constantly changing and the formula doesn't hold anymore.
In your case, you are regenerating int z everytime the loop is called,
All you have to do is define z outside the loop and instantiate z as 1 and also, you are not retaining the previous values of z so that's why it wasn't working. So it should be z = z + j and put this line below the print statement and you are done.
Here is an snippet of code which would help you my way:
int j = 1;
for(int i=1; i<=numberOfElements; i++) {
System.out.println(j);
j = j + 2*i;
}
And, here is an snippet of code which would help you your way:
int j = 0;
int z = 1;
for (int i = 1; i <= numberOfElements; i++)
{
j = i * 2; // + by how much
System.out.print(z + " ");
z = z + j; //sum
}
Note the trend.
You are adding a multiple of 2 to the previous number to get the next number. The multiple of 2 to be added depends upon the position of the number. For example, to get the 1st number, you add 2 x 0 to 1. To get the 2nd number, you add 2 x 1 to the previous number (that gives 3). To get the 3rd number, you add 2 x 2 to the previous number (that gives 7). To get the 4th number, you add 2 x 3 to the previous number (that gives 13).
To get the number at nth position, you add 2 x (n-1) to the previous number.
Now take a look at the example below, keeping the above explanation in mind.
public static void printSeparatorSequence(int numberOfElements) {
int number = 1;
for (int i = 0; i<numberOfElements;i++) {
number = number + 2 * i;
System.out.print(number);
}
System.out.println();
} //end of method printSeparatorSequence
} // end of class
This is the solution of your problem. I have discussed the code by the comment lines given within the code.
public class DistanceSeparator
{
/* Main Method */
public static void main(String[] args)
{
/* printSeparatorSequence Function is Called */
printSeparatorSequence(3);
printSeparatorSequence(5);
printSeparatorSequence(8);
}
/* printSeparatorSequence Function Definition */
public static void printSeparatorSequence(int NumberOfElements)
{
/* variable j is used to get the multiples of
2 by multiplying with variable i within the for loop
and variable sum is used to get the total value */
int j=2,sum=1;
for(int i=0;i<NumberOfElements;i++)
{
sum=sum+(j*i);
/* Here total sum is printed with a space */
System.out.print(sum+" ");
}
/* It is used for new line */
System.out.println();
}
}
Related
I am new to programming and I have an exercise that's killing me. How can you print a grid (5-by-6) which consists of asterisks alone? [Later on, these asterisks will have to be replaced by letters which are read in with StdIn.readInt() and a switch statement, but for now I at least need to understand how to print the grid]. I would appreciate any help so much!
More specifically, the grid should look like this:
//THIS ISN'T THE CODE; JUST AN ILLUSTRATION OF WHAT SHOULD BE PRINTED
0 1 2 3 4 5
0 * * * * * *
1 * * * * * *
2 * * * * * *
3 * * * * * *
4 * * * * * *
//I AM SUPPOSED TO START WITH SOMETHING LIKE THIS:
public class Grid {
static int X = 6;
static int Y = 7;
public static void main(String[]args) {
int [][] grid = new int [X][Y];
This could have been done in many ways, but this is my way of doing it:
When you want to print a grid, you have to use 2 nested for loops.
Let's see what happens when you use 2 nested for loops:
for(int i = 0; i < 6; i++){
for(int j = 0; j < 7; j++){
}
}
We start with the first loop:
for i = 0, we will enter the second loop and iterate from 0 to 6.
for i = 1, we will enter the second loop and iterate from 0 to 6.
...
for i = 5, we will enter the second loop and iterate from 0 to 6.
What you should notice is that j will iterate and take values from 0 to 6 with each value of i.
Going back to your question, and comparing it by what i just showed, you should notice that for each line, you are printing 7 values (of a column).
Let's assume i is the number of lines, and j is the index of each value in that line (column).
public static void printGrid() {
for (int i = 0; i < 6; i++) {
System.out.println();
for (int j = 0; j < 7; j++) {
System.out.print("*");
}
}
}
This code prints on each line (i), 7 asterixes (j).
And each time i is incrementing, we are going back to the next line System.out.println(). That's why we put it inside the for loop with i.
In your situation, we have to tweak this code a little bit to be able to print the numbers on the sides, and that space at the top left corner.
The explanation is in the comments in my code.
public class Question_55386466{
static int X = 6;
static int Y = 7;
public static void printGrid() {
System.out.print(" "); // Printing the space on the top left corner
for (int i = 0; i < X; i++) {
if (i > 0) { // Printing the numbers column on the left, taking i>0 to start from the second line (i == 1)
System.out.println(); // Going to the next line after printing the whole line
System.out.print(i - 1);//Printing the numbers of the column. Taking i-1 because we start the count for i == 1 not 0
}
for (int j = 0; j < Y; j++) {
if (i == 0)
System.out.print(j + " ");//Print the first line numbers.
else
System.out.print(" * "); //if the line isn't the first line(i == 0), print the asterixes.
}
}
}
You can always edit the values of X and Y and get the desired result.
And later you can give this method your array as a parameter and print each element instead of the asterixes.
The problem is that there is no output happening, not an extra println(). This is odd, because doing this programming without a static SIZE var, it works just fine.
public class SlashFigure2
{
public static final int SIZE = 4;
public static void main(String[] args)
{
for(int i = 1; i <= SIZE; i++)
{
for(int j = 1; j <= 2 * i - (2 * SIZE + 2); j++)
{
System.out.print("\\");
}
for(int j = 1; j <= -4 * i + (-4 * SIZE + 2); j++)
{
System.out.print("!");
}
for(int j = 1; j <= 2 * i - (2 * SIZE + 2); j++)
{
System.out.print("/");
}
System.out.println();
}
}
}
In case anyone needs it, here's what the program prints:
!!!!!!!!!!!!!!
\\!!!!!!!!!!//
\\\\!!!!!!////
\\\\\\!!//////
EDIT: Here's what the site keeps saying is the error
EDIT 2:
The site is practiceit.csu.washington.edu
Here is the question's wording:
Modify your DollarFigure program from the previous exercise to become
a new program called DollarFigure2 that uses a global constant for the
figure's height. (You may want to make loop tables first.) The
previous output used a constant height of 7. The outputs below use a
constant size of 3 (left) and 5 (right)
Here are the outputs below they are talking about
(You must solve this problem using only ONE public static final
constant, not multiple constants; and its value must be used in the
way described in this problem.)
Simply do this:
if (i != SIZE) {
System.out.println();
}
Because i will be equal to SIZE in the last iteration, and you want to skip the println() in that case.
UPDATE
From the comments and the image, it's clear that you're not supposed to define SIZE as a constant, apparently you should be able to pass n as a parameter to your program, it's not a hardcoded value. Check the rules of the "site" you keep referring to, how's the input supposed to be received?
You can make this change in your code to make it work.You should not execute the statement when i is equal to SIZE
if(i<SIZE){
System.out.println();
}
Somewhat Jeopardy to find out the actual problem/quest you want to solve by algorithmically print a specific ASCII-art only denoted by a constant ROW-size (e.g. 4 or 6 as depicted on the attached image).
Tests & sample output
Derived specification
Draw a specific figure varying only in its height:
only single parameter is passed: rows of ASCII-art to draw
figure to draw should resemble a downward-arrow
bordered by double-slashes left and right, i.e. \\ respective //
no border/slashes on the first row
inner/rest of the rows filled with exclamation-marks !!
at least 2 exclamation-marks !! on the inner last row
Java method with single parameter: ROWS
private static void drawAsciiArt(int rows) {
int columns = (rows-1)*4+2;
for(int i = 1; i <= rows; i++) {
int borderSize = (i-1)*2;
int fillSize = columns - borderSize*2;
for(int j = 1; j <= borderSize; j++) {
System.out.print("\\");
}
for(int j = 1; j <= fillSize; j++) {
System.out.print("!");
}
for(int j = 1; j <= borderSize; j++) {
System.out.print("/");
}
if (i < rows) {
System.out.println();
} // if not last row
} // end of row-loop
}
Try this online
Figured it out! It turns out that for both the '\' and '/' characters, I didn't need to use that (x * SIZE + y) formula after all. They both needed the regular formula while the '!' is the only character that needed the SIZE formula
public class SlashFigure2
{
public static final int SIZE = 4;
//program works no matter what value SIZE holds
public static void main(String[] args)
{
for(int i = 1; i <= SIZE; i++)
{
for(int j = 1; j <= 2 * i - 2; j++)
{
System.out.print("\\");
}
//note the SIZE formula in here
for(int j = 1; j <= -4 * i + (4 * SIZE + 2); j++)
{
System.out.print("!");
}
for(int j = 1; j <= 2 * i - 2; j++)
{
System.out.print("/");
}
System.out.println();
}
}
}
i have to make a program that prints out the elements of an array filled with random numbers backwards but it also prints out a zero after my variables? i think it has something to do with my for-loops but i get a java.lang.ArrayIndexOutOfBoundsExceptionerror any time i try to change them.
edit: i also noticed that the first printed element is always zero. i don't really see it as a problem but what could be causing that?
import java.util.*;
public class EZD_printBackwards
{
static int vars[] = new int[10];
static int backwards()
{
Random rand = new Random();
int bkwds = vars[0];
for (int a = 0; a < 10; a++)
{
vars[a] = rand.nextInt(100)+1;
}
for (int x = 10; x > 0; x--)
{
System.out.println("Element " + x + " is " + vars[x] );
}
return bkwds;
}
public static void main(String Args[])
{
int option;
Scanner kbReader = new Scanner(System.in);
do
{
System.out.println(backwards());
System.out.print("Type 1 to run again. Type 0 to end the program.");
option = kbReader.nextInt();
while(option !=1 && option !=0)
{
if (option != 1 && option != 0)
{
System.out.print("Please enter 1 to run again or 0 to end the program.");
option = kbReader.nextInt();
}
}
}while(option==1);
System.out.println("");
}
}
In your example, vars is size 10. The second for loop starts at index x = 10 which is greater than the last index of vars because array index starts at zero. To fix the issue, you should use this condition in your for loop:
for (int x = vars.length -1; x >= 0; x--)
{
System.out.println("Element " + x + " is " + vars[x] );
}
You have two problems:
FIRST => For loop out of bounds
you want to go through 10 elements, therefore your
for (int x = 10; x > 0; x--)
should be
for (int x = 9; x >= 0; x--)
0..9 is 10 elements and the same things goes for
for (int a = 0; a < 10; a++)
to
for (int a = 0; a < 9; a++)
SECOND ==> 0 at the end
That's because you do
System.out.println(backwards());
instead of
backwards();
you are returning the value of "bkwds", and you are initializing "bkwds" with vars[0] , and i guess in java the compiler initialize all the values of an array with 0 ,
in other words your probleme is in System.out.println(backwards());
remove it with
backwards();
and it should work !
EDIT
your look is out of bound either replace it with this
for (int a = 0; a < 10; a++)
or
do this
for (int a = 9; a > 0; a--)
The range of your Array is from 0 up to and including 9. Your for loop, however, is starting from 10 and coming down to index 1. It should start from 9 and comes down to index zero. This, however, does not explain printing random 0! The reason for these zeros is you have an int bkwds which youb set to vars[0] at the beginning of your function. But, since it is not initialized, it will be set to 0 (the default for int) In your main, you call the function in a print statement, which I suppose keeps printing that falsely, useless initialized variable that you return :)
As arrays are indexed from zero, change to
System.out.println("Element " + x + " is " + vars[x-1] );
output
Element 10 is 31
Element 9 is 63
Element 8 is 82
Element 7 is 46
Element 6 is 67
Element 5 is 24
Element 4 is 3
Element 3 is 27
Element 2 is 37
Element 1 is 13
edit
And change this
System.out.println(backwards());
to
backwards();
As the return value of this method is useless and not used, change this method to return void
I've been trying to make the following for loops to print the original and modified values of an array in two columns, separated by \t\t. Here is my code:
public class Main {
public static void main(String[] args) {
int jay[] = {1,2,3,4,5,6};
System.out.println("Original\tAfter");
for(int y: jay) {
System.out.println(y);
}
multiplyByTen(jay);
for(int z: jay) {
System.out.println("\t"+ z);
}
}
public static void multiplyByTen(int x[]) {
for(int counter = 0; counter<x.length;counter++) {
x[counter] *= 10;
}
}
}
This is the result so far:
Original After
1
2
3
4
5
6
10
20
30
40
50
60
So my question is how to align the value 10 to 1, and 20 to 2 and so on?
This is the solution of your problem, but i don't know if this is exuctly what you want, but it gives you the wished result
public class Main {
public static void main(String[] args){
int jay[] = {1,2,3,4,5,6};
int jay2[] = jay.clone();
multiplyByTen(jay);
for(int i = 0; i < jay.length;i++) {
System.out.println(jay2[i]"\t"+ jay[i]);
}
}
public static void multiplyByTen(int x[]){
for(int counter = 0; counter<x.length;counter++) {
x[counter] *= 10;
}
}
}
This example is from thenewboston java series, I just modified it a bit to see if I can print an original and after arrays side by side.
There is no way to print it side by side with your current construct because array gets manipulated and changed when passed into the method. One of the only ways would be making a copy of the original and print both original and after in the same line.
If your multiplyByTen method accepts a single int value you can do it as:
for(int y : jay)
System.out.println(y + "\t" + mutiplyByTen(y));
If your multiplyByTen method returns an int array, you can do it as:
int[] arr = mutiplyByTen(jay);
for(int x=0; x<jay.length; x++)
System.out.println(jay[x] + "\t" + arr[x]);
But with the current method signature, you need to make another copy of the original array.
My solution using a single array:
public class Main
{
public static void main(String[] args)
{
int jay[] = { 1, 2, 3, 4, 5, 6 };
System.out.println("Original\tAfter");
multiplyByTen(jay);
// To verify values in the original array (you can remove this loop)
for (int z : jay)
{
System.out.println(z);
}
}
public static void multiplyByTen(int x[])
{
for (int counter = 0; counter < x.length; counter++)
{
System.out.print(x[counter] + "\t\t");
x[counter] *= 10;
System.out.println(x[counter]);
}
}
}
OUTPUT
Original After
1 10
2 20
3 30
4 40
5 50
6 60
If you were to use a enhanced loop inside the multiplyByTen(int x[]) method, you would only be changing the local value and not the value in the array. So, if you were to print out the values in the original array, they would remain the same as the original. This way, the values in the array are permanently modified. So, printing the values after the method will show the multiplied values.
Lastly, I would not use print() or println() methods for this. I would use printf() to print out a formatted output. You will find that tabbing will eventually result in misaligned columns (when the number of digits gets larger). You would not run into this issue when using printf().
Keep it simple.
Why not simply do
for(int y : jay) {
System.out.println(y + "\t" + y*10);
}
It is far better to use Arrays.copyOf(...) when you think of using .clone()1:
int jay[] = {1,2,3,4,5,6};
int jay2[] = Arrays.copyOf(jay,jay.length);
System.out.println("Original\tAfter");
multiplyByTen(jay2);
for (int i = 0; i < jay.length; i++) {
System.out.println(jay[i]+"\t\t"+jay2[i]);
}
This way, you print table rows and not columns.
1Why you should never use .clone() for defensive copying.
I would like to understand, why is it when I specify the number for the method to sum up numbers it returns 21, but when i enter the value through scanner it gives me the correct value. For example number 3 should be 1 + 2 + 3 = 6 but its giving me 21, any ideas thanks.
public class sumInt
{
public static void main(String[] args)
{
int i = sumInt(3);
int j = sumInt(10);
Scanner in = new Scanner (System.in);
System.out.println("Please enter posiutive integer: ");
int k = in.nextInt();
System.out.println(sumInt(i));
System.out.println(sumInt(j));
System.out.println(sumInt(k));
}
public static int sumInt(int n)
{
int sum = 0;
for (int i = 0; i <= n; i++)
{
sum += i;
}
return sum;
}
}
You are actually summing up to 6 for i, your current code could also be written as:
System.out.println(sumInt(sumInt(3)));
You'll need to print out i directly instead of calling sumInt on it again.
When you first do int i = sumInt(3);, i gets set to 6 (1 + 2 + 3). When you System.out.println(sumInt(i)), it does sumInt(6), which is 21, because you haven't reset i to 3.
To see the actual results, you should change what you're outputting to:
System.out.println(i);
System.out.println(j);
System.out.println(sumInt(k));
Or change your initial definitions of i and j to:
int i = 3;
int j = 10;
It's because you're calling sumInt in two places, when you only meant to call it in one:
int i = sumInt(3); // sets i = sumInt(3) == 6
System.out.println(sumInt(i)); // prints sumInt(i) == sumInt(6) == 21
Because you're calling sumInt() twice; once at the beginning, then again in the print statements.
You are saying i = sumInt(3) so i == 6.
Then your print sumInt(i) == sumInt(6) which I'm guessing is 21..
You call sumInt twice for the same number.
int i = sumInt(3); //i gets 6
System.out.println(sumInt(i)); //called with 6 =21
This is because of the following lines
System.out.println(sumInt(i));
System.out.println(sumInt(j));
System.out.println(sumInt(k));
You are already calculating i and j as the sum of the integers you want, and when you printout , you are again calculating sum of i and j
change the above three lines to the following:
System.out.println(i);
System.out.println(j);
System.out.println(sumInt(k));