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I am trying to write the following program sequence.
The first three numbers in the sequence are 1, 1, 2. Every other number in the sequence is the sum of the three previous numbers. The program should prompt the user to enter a limit; the program will stop when the current number in the sequence is greater than or equal to this limit.
For example if I write the limit being 123 I should get: 1 1 2 4 7 13 24 44 81
I tried the following:
import jpb.*;
public class XiaolinSequence {
public static void main(String[] args) {
SimpleIO.prompt("Enter a limit on the largest number to be displayed:");
String userInput = SimpleIO.readLine();
int counter = Integer.parseInt(userInput);
int older = 1;
int old = 1;
int current = 2;
while (current < counter) {
int nextNumber = older + old + current;
older = old;
old = current;
current = nextNumber;
System.out.println(nextNumber);
}
}
}
But I am having trouble getting the sequence to print out.
You need to change how you print things.
The missing 1 1 2 are never printed because they are never stored in nextnumber, the only variable you ever print.
You will get an additional 149 because you print nextnumber without checking it its value is greater than the limit.
For me the output of the following code is 1 1 2 4 7 13 24 44 81 all on new lines.
int counter=123; // replaced IO code so I did not have to download the jar.
int older=1;
int old =1;
int current=2;
System.out.println(older); // prints the first 1
System.out.println(old); // prints the second 1
System.out.println(current); // prints the 2
while(current<counter){
int nextnumber=older+old+current;
older=old;
old=current;
current=nextnumber;
if(nextnumber <= counter)
{
System.out.println(nextnumber);
}
}
Ok since people bashed me for your SimpleIO, use whatever you want to read the input. Instead, I'm going to point out a logic flaw in your code.
For the program to function correctly, you need to print out older instead of current, like so:
while (older < counter)
{
System.out.println(older);
final int nextnumber = older + old + current;
older = old;
old = current;
current = nextnumber;
}
It works just fine.
There is no such thing as SimpleIO in java.lang.
You may want to replace String userInput = SimpleIO.readLine() with
System.out.print("Enter limit: ");
Scanner in = new Scanner(System.in);
String userInput = in.next();
then the code will work.
Oh and by the way, don't forget to print out 1 1 2 before you start the loop.
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So i got problem in java to determine who the last kid who got the candy, n is how many children, m is how many candy, and s is the number of kid who got the first candy.
so basically if n =4, m=6, and s =2 the answer is 3, because all started from 2(number of kid who got the first candy)->3->4 and restart to 1->2->3 and 3 is the last kid who got the candy.
the code run perfectly but i encounter bug at n = 3333, m =3333, and s = 1
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
int m = in.nextInt();
int s = in.nextInt();
int total = m%n;
int jaw = total+s-1;
System.out.print(jaw);
}
I assume the "bug" you're mentioning is that jaw is 0, right? That's because 3333%3333 will be 0 and thus 0 + s - 1 will be 0 as well (0+1-1 = 0).
You're on the right track, i.e. m % n would tell you how many pieces of candy are left after everyone got a fair/equal share.
Now you just distribute the "rest" (total) which means you "add" it to "first child" (s). Let's say this is c = s + total, so c is the last child that got anything. You subtract -1 because if you add anything the "cursor" advances to the next child and thus you want to track back.
However, what if you didn't have anything to distribute? Then the last child that got anything was the one before the first, which in case of 4 children and starting at 1 would be the 4th. Your calculation results in 0 which basically would express this.
Another problem you might face with your code is that if you start at the last child (say 4) and have 2 pieces of candy to distribute, then you'd get the "5th" child instead of the "1st" to be the last to get something: 2 + 4 - 1 = 5.
So how do you solve that?
Add jaw %= n to handle the "overflow" (if you start at the last child and distributed 2 more pieces of candy, the first would get it)
Check if jaw == 0 in which case the solution would be jaw = n (the last child got the last candy)
The problem is that you arrive at person 0 , who does not exist.
3333%3333 = 0
then 0 + 1 - 1 = 0
As we are in a loop 0 is the last person of the previous turn ie person number m.
We solve this by saying that, if the result is zero we return m.
import java.util.Scanner;
class sweets {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
int m = in.nextInt();
int s = in.nextInt();
int total = m%n;
int jaw = total+s-1;
if(jaw == 0){
jaw = m;
}
System.out.print(jaw);
}
}
You need to consider whenever m%n==0.
In that case jaw= n-s+1;
Just need to add an if statement to include it.
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PROBLEM DESCRIPTION
Peter wants to generate some prime numbers for his cryptosystem. Help him! Your task is to generate all prime numbers between two given numbers!
Input
The input begins with the number t of test cases in a single line (t<=10). In each of the next t lines there are two numbers m and n (1 <= m <= n <= 1000000000, n-m<=100000) separated by a space.
Output
For every test case print all prime numbers p such that m <= p <= n, one number per line, test cases separated by an empty line.
Example
Input:
2
1 10
3 5
Output:
2
3
5
7
//----------BLANK SPACE BETWEEN TEST CASES-------------
3
5
import java.util.*;
import java.lang.*;
class Main
{
public static void main (String[] args) throws java.lang.Exception
{
Scanner in = new Scanner(System.in);
int t = in.nextInt();
for(int i=0;i<t;i++)
{
boolean prime = true;
long m = in.nextLong();
long n = in.nextLong();
if(m<2)
{
System.out.println("2");
m=3;
}
for(int j=m;j<=n;j+=2)
{
int z = (int)Math.floor(Math.sqrt(j));
for(int k=2;k<=z;k++)
{
if(j%k==0)
{
prime=false;
break;
}
}
if(prime)
System.out.println(j);
}
System.out.println();
}
}
}
Your loops are using int datatype. It is lossy because you are comparing long with int. It will work for small numbers but constraints are too big so try using long.
Edit
I thought its because overflow without running it.
Your code has lots of problems
It will not work when m is even
you are not setting prime back to true in loop
Check these suggestions and comment is it working?
Solution
use long datatype in loop (that is not necessary)
set prime = true in inner loop
instead of incrementing by 2 i.e. j+=2, increment by 1 j+=1.
My homework is to create a program that takes a list of numbers and prints out the highest number divisible by four.
List would look like this:
12
16
87
58
25
73
86
36
79
40
12
89
32
Input should be:
40 because it is the highest number there divisible by four.
Here is my code:
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int saved = 0;
int saved2 = 0;
for (int i = scanner.nextInt(); i % 4 == 0; i = scanner.nextInt()) {
for (boolean bull = true; bull == true; bull ^= true) {
if (i > saved) {
saved -= saved2;
saved += i;
saved2 += i;
}
}
System.out.println(saved);
}
}
}
The input of my code is
12
16
I don't really understand why this is doing it, but it seems to me that I'm adding the variables wrong. The homework page on adding variables does not specify how to add variables to each other.
Does anyone have a tip to improve the code in anyway, or find a way to make a fix my code? Thank you.
welcome to Java.
First you are saying you got input, but that is output. Input is what you enter, and output is what you get printed.
Then there is a mistake in your for loops. You have too much going on in one place. By the logic which is implemented, your program will exit first level for loop whenever your entered value is not divisable by 4.
Read on for loops if you want to learn more https://www.learnjavaonline.org/en/Loops.
I recommend to start from while loops instead. The logic whould be this:
1. create variable to hold the correct answer saved
2. create another one to hold the value read from console i
3. start the while loop with condition i = scanner.nextInt()
3.1 check if the value just entered i is divisable by 4
3.2 if it is, then compare if it's larger than the one was saved before (initially saved value will be 0)
3.3 if it is larger, then assign the read value i to the saved
4. At the end of the loop, you will have the highest number divisable by four in your saved variable. Print it.
I will provide some help, according to
How do I ask and answer homework questions?
for (int i = scanner.nextInt(); i % 4 == 0;i = scanner.nextInt())
This only reads as long as ALL inputs are divisible by 4, that is why it ends at 16, because 87 is not divisible by 4.
for (boolean bull = true; bull == true ;bull ^= true)
This needs explanation by you, but I am pretty sure that it unconditionally executes the body of the inner loop exactly once. (Not 100% sure, because the representation of true and false could be weird in your machine. Should 0 be the representation of true, i.e. really weird, then it is an endless loop, which does not match the output you describe...)
System.out.println(saved);
This executes exactly once per input, except the last one, which is not a multiple of 4.
The value of saved is identical to input, as long as it is increasing.
These hints explain the unexpected output.
If you inspect the details of what the problem is, you should be able to improve your coding attempt.
This is how I super-quickly fixed in your code.
Note that there are no statements about the possible minimum value and about how do you stop the input. Therefore the solution is pretty-straightforward, it just reads the input until integers are present there.
This article may be useful about handling the input from the Scanner.
I hope the comments in the code will help. Add comments if there are any questions. Good luck!
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int currentMax = Integer.MIN_VALUE; // you may set negative or 0 if you know that all the input is positive
// int saved2 = 0; // no need for this variable
while (scanner.hasNextInt()) { // you can make a better input handling, especially if you know when it should end the input. Now it will end on any non-integer input line
int i = scanner.nextInt();
// for (int i = scanner.nextInt(); i % 4 == 0; i = scanner.nextInt()) {
// for (boolean bull = true; bull == true; bull ^= true) {
if (((i % 4) == 0) && (i > currentMax)) {
currentMax = i;
// saved -= saved2;
// saved += i;
// saved2 += i;
// }
}
}
System.out.println(currentMax); // moved out of "for" or "while" cycles. Print the value after the input has ended.
}
}
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Edit: I have found a way to work with CompareTo to help with this problem, but for some reason I cannot get the count down to work.
It's a negative number that needs to get more negative to meet the requirements, but I am missing something here. When I execute the down section it closes the program. So to me this means that I have something messed up and the program isnt seeing the problem and closing.
We are supposed to:
Ask the user for an integer then ask the user if he/she wants to count
up or down. Display a table of numbers where the first column contains
the counter, the second column contains the counter plus 10, and the
third column contains the counter plus 100. Make it so each number
takes up 5 spaces total.
If counting up, the first column should contain numbers 1 through the
user input; If counting down, the first column should contain numbers
-1 through the the negative of the user input;
Do user input validation on the word "up" and "down". Allow for any
case.
import java.util.Scanner;
public class ps1 {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
//Comparision string already declared
String up = "up";
String down = "down";
//initialize the counters sum
int sum = 0;
//ask the user for a number
System.out.println("Enter an ending value");
int num1 = keyboard.nextInt();
keyboard.nextLine();
System.out.println("Count up or down?");
String input = keyboard.nextLine();
while (input.equalsIgnoreCase(up) || input.equalsIgnoreCase(down)) {
System.out.println("Count up or down?");
input = keyboard.nextLine();
}
if (input.compareToIgnoreCase(up) == 0) {
if (num1 >= 0)
for (int c = 1; c <= num1; c++) {
sum = sum + c;
System.out.printf("%5d%5d%5d\n", c, c + 10, c + 100);
else
System.out.println("Up numbers must be positive");
if (input.compareToIgnoreCase(down) == 0) {
for (int c1 = -1; c1 <= num1; c1--) {
sum = sum + c1;
System.out.printf("%5d%5d%5d\n", c1, c1 + 10, c1 + 100);
}
}
}
}
}
I see you have figured out core logic. BTW, your code will not compile, there is a syntax error.
Your code would look like this:
print(a a+10 a+100)
I know that it's not valid syntax but you would be able to figure out the correct way to write the code.
To print data properly, you will need following:
https://dzone.com/articles/java-string-format-examples
I would recommend visualizing the output first. In your case, it would look like following: (_are spaces)
Enter an ending value: 2
Direction: Up
____1___11__101
____2___12__102
Also, think about error cases. What will happen in following:
Enter an ending value: -10
Direction: Up
Error: Improper data
You are allowing user to enter a positive num1 and count down using for (int counter1 = -1; counter1 >= num1; counter1--). This makes no sense as counter1 >= num1 resolves to -1 >= 1 which is never true. When direction is down the number must be negative and when direction is up the number must be positive.
You might need to loop until user provides a valid direction. Currently you go down for any input that is not up. A possible solution would be to:
String input;
do {
input = keyboard.nextLine();
} while (!input.equalsIgnoreCase("up") && !input.equalsIgnoreCase("down"));
Please use shorter variable names. counter1 is scoped just to the for loop block so call it i. It's easier to read.
Whichever editor you are using configure auto formatting :)
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(I am using Java 1.4.2) I wanted to have an array that should flip a 'coin' a certain amount of times given by the user (the coin can flip up to 1000 times). Then randomly generate an integer between 1 and ten, store all the numbers in an array. I have the following code but it keeps on giving me the following error:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 7
at CoinFlip.main(CoinFlip.java:42)
Here is the code I wrote.
import java.io.*;
import java.math.*;
public class CoinFlip
{
public static void main(String[] args) throws IOException
{
// setting up variables
String timesString;
int times;
// setting up input
BufferedReader in;
in = new BufferedReader(new InputStreamReader(System.in));
do
{
// times will display how many times the coin will flip
// loop if times does not fulfill the requirements
System.out.println("How many times do you want the coin to flip? (MUST be an integer between 1 to 1000)");
timesString = in.readLine();
// convert timesString into an integer
times = Integer.valueOf(timesString).intValue();
if((times > 1000)||(times < 1))
{
System.out.println("ERROR: The number of times you flip the coin must be an integer between 1 and 1000.");
}
System.out.println("The value for times is " +times);
}
while((times > 1000)||(times < 1));
// create a new array
double flip[] = new double[times];
// create a new variable timeStore that sets the boolean conditions for the For Loop
int timeStore;
for(timeStore = 0; timeStore <= times-1; timeStore++)
{
System.out.println("timeStore (how many iterations) is " +timeStore);
System.out.println("FOR LOOP: When " +timeStore+ " is less than or equal to " +(times-1));
flip[times] = Math.round(Math.random()*9)+1;
// the line above stores a random integer between 1 and 10 within the current index
System.out.println("flip["+times+"] = "+flip[times]);
}
}
}
At line 42;
flip[times] = Math.round(Math.random()*9)+1;
Should be;
flip[timeStore] = Math.round(Math.random()*9)+1;
Then also in the System.out on line 44.
These are wrong:
42: flip[times] = Math.round(Math. random()* 9 ) + 1;
44: System.out.println("flip[" + times + "] = " + flip[times]);
It appears you meant
42: flip[timeStore] = Math.round(Math.random()*9)+1;
44: System.out.println("flip["+timeStore+"] = "+flip[timeStore]);
Since you declared flip as an array of size times, only indices 0...(times - 1) are valid. In particular, index times is invalid and so flip[times] will throw.
Note that the compiler was telling you the offending line, and the offending index passed in. It's telling you you passed in 7 as the index. But note, this exception is happening on the first iteration of your loop. You can tell this by the output that your program would have produced since you have helpful print debugging statements in your code. Thus, you should have been able to reason: hey, why is my array seeing the index 7 on the first iteration of the loop when the index should be 0? At that point, the error practically figures itself out.
Also, idiomatic usage of arrays is:
for(timeStore = 0; timeStore < times; timeStore++)
but even better is:
for(timeStore = 0; timeStore < flip.length; timeStore++)