Returning a Correctly Sized Array for Dive Moves

  • Context: Java 
  • Thread starter Thread starter testme
  • Start date Start date
  • Tags Tags
    Array Java
Click For Summary

Discussion Overview

The discussion revolves around the challenge of returning a correctly sized array in a Java program that tracks a diver's movements. Participants explore how to handle arrays that may not be fully populated and how to return only the relevant portion of the array that contains meaningful data.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant inquires whether it is possible to return an array that only includes the filled portion, questioning how to handle an array that is not completely filled.
  • Another participant asks for clarification on the programming language being used, indicating that the answer may depend on that context.
  • A participant provides a Java code example demonstrating how to extract the filled portion of an array, suggesting that while it is possible, it may not be the most sensible approach compared to using strings.
  • There is a question raised about whether the size of the array is determined at runtime or known beforehand, indicating a potential concern about managing array sizes.
  • A participant shares a detailed program that simulates a diving scenario, explaining the logic behind how moves are recorded and how the program checks if a dive occurs based on the last element of the array.
  • Another participant reiterates the diving program's logic, emphasizing the need to handle the array's length correctly to avoid issues with uninitialized elements affecting the dive check.

Areas of Agreement / Disagreement

Participants express varying opinions on the best approach to handle the array size and contents. There is no consensus on whether returning a filled array is the best practice, and the discussion remains unresolved regarding the optimal solution.

Contextual Notes

Participants mention constraints such as not being allowed to use strings, which may limit the methods available for handling the array data.

testme
Messages
68
Reaction score
0
If I have a program where I need to return an array, is it possible that I only return the array with the length of what was added to it?

What I mean is I have an array that gets filled up with letters but it doesn't always get completely filled up.

Is there a way I can only return the filled up part (including having only it's size)

Ex: array[4] = {?, ?, ?, ?, ?}

fills up to array[4] = {F, B, F, G,?}

and when I return it I only want an array like this

arr[3] = {F, B, F, G}
 
Technology news on Phys.org


testme said:
If I have a program where I need to return an array, is it possible that I only return the array with the length of what was added to it?
It's hard to answer your question without knowing what language you are writing code in.
testme said:
What I mean is I have an array that gets filled up with letters but it doesn't always get completely filled up.

Is there a way I can only return the filled up part (including having only it's size)

Ex: array[4] = {?, ?, ?, ?, ?}
Why do you have 5 question marks in an array that has 4 elements?
testme said:
fills up to array[4] = {F, B, F, G,?}

and when I return it I only want an array like this

arr[3] = {F, B, F, G}
 


Oops, sorry, it's late at night here. I'm using Java and bump those up 1. I was thinking as though I'm reading an element from the array.
 


testme said:
If I have a program where I need to return an array, is it possible that I only return the array with the length of what was added to it?

What I mean is I have an array that gets filled up with letters but it doesn't always get completely filled up.

Is there a way I can only return the filled up part (including having only it's size)

Ex: array[4] = {?, ?, ?, ?, ?}

fills up to array[4] = {F, B, F, G,?}

and when I return it I only want an array like this

arr[3] = {F, B, F, G}

Possible, yes (see below, for example). Sensible, probably not. Why work with arrays of Letters instead of a String? What exactly are you trying to do?

Code: 
import java.util.Arrays;

public class ArrayTest {

	public static void main(String[] args) {
		char[] testArray = {'F', 'B', 'F', 'G','?'};
		char[] filledArray = getFilledArray(testArray);
		for(char c : filledArray) {
			System.out.println(c);
		}
	}
	
	private static char[] getFilledArray(char[] inputArray) {
		String str = Arrays.toString(inputArray);
		str = str.replaceAll("[\\[\\]? ,]", "");
		char[] outputArray = str.toCharArray();
		return outputArray;
	}
	
}
 
Last edited:


Is the size of this object determined at run-time or known before hand?
 
Here is my program so you can see what I need. This program is supposed to check if a person dives on a diving board or doesn't because of their nerves. Every step they take is 2 feet and they have to move 10 feet to dive. If they have nerves and step back they move back 2 feet.

Code: 
/**
 * This program will determine whether a person will dive or not using
 * the probability of someone to jump due to nerves
 */

class Dive 
{
  public static void main (String args[ ])
  {
    // DECLARE VARIABLES/DATA DICTIONARY
    int tMax; //the maximum number of seconds the diver has to dive
    char[] moves; //reference to a character array showing the sequence of man’s moves
    int num; //the number of seconds taken by the diver to dive
    char again; //the character that will determine whether  the user wants to run another trial

    System.out.println("Diving Chance");
    do
    {
    System.out.println("Please enter the maximum time in seconds to make a dive: ");  
    
    // READ IN GIVENS use our ITI1120 special class for keyboard input 
    tMax = ITI1120.readInt(); //reads in the user's choice
    
    // BODY OF ALGORITHM - Call to the method to solve problem
    moves = dive(tMax); //call to the method
    num = moves.length; //gets the length of the array and removes 1 
    
    // PRINT OUT RESULTS AND MODIFIEDS
    if(moves[num - 1] == 'D') //checks to see if the man dived or not
    {
      System.out.print("The man jumped with the moves ");
      for(int i = 0; i < num; i++) //loop that goes through the array of moves and prints each letter out
      {
      System.out.print(moves[i]);
      }
      System.out.println(" in "+num+" seconds");
    }
    /*else
    {
      System.out.print("The man lost his nerves after the moves ");
      for(int i = 0; i < num; i++) //loop that goes through the array of moves and prints each letter out
      {
      System.out.print(moves[i]);
      }
      System.out.println();
    }*/
    System.out.println("Do you wish to make another dive attempt? (y/n): ");
    again = ITI1120.readChar(); //reads in user's input for starting another run
    if(again == 'n')
    {
      System.out.println("Program terminated!");
    }
    }while(again == 'y');
  }
  
  // Problem Solving Method
  // Description: Determines if the man dives or not
  // Parameters (GIVENS): 
  //    tMax - the maximum number of seconds the diver has to dive
  public static char[] dive(int tMax)
  {  
    // DECLARE VARIABLES/DATA DICTIONARY
    
    // INTERMEDIATES
    int x = 0; //the man's distance in feet
    int index = 0; //the index number for the element in the array
    double p; //the probability of taking a step forward
    double ranNum; //a random number
    
    // RESULT
    char diveRes[] = new char[tMax]; //an array that holds the moves takens, F - foward, B - backward, D - dive
    
    // BODY OF ALGORITHM
    while(index < tMax && x < 10) //keeps going as long we haven't exceeded the maximum time allowed or the man hasn't dived
    {
      ranNum = Math.random(); //creates the random number from 0.0 to 1.0
      p = 1.0 - (x/10.0); //calculates the probability 
      if(ranNum < p)
      {
        x = x + 2;
        diveRes[index] = 'F';
      }
      else
      {
        if(x != 0)
        {
        x = x - 2;
        }
        diveRes[index] = 'B';
      }
      index++;
    }
    if(x == 10) //sets the last element in the array to D if the man dives
    {
      diveRes[index - 1] = 'D';
    }
    // RETURN RESULT
   return diveRes;
  }
  
} // Don't remove this brace bracket!

Where my problem lies is in the main method where I'm checking if moves[num-1] == 'D' because num is getting the length of the full array which has a bunch of garbage at the end so it doesn't know that the last letter really was a D.

We were also told we're not allowed to use strings.
 
Last edited:
testme said:
Here is my program so you can see what I need. This program is supposed to check if a person dives on a diving board or doesn't because of their nerves. Every step they take is 2 feet and they have to move 10 feet to dive. If they have nerves and step back they move back 2 feet.

Code: 
/**
 * This program will determine whether a person will dive or not using
 * the probability of someone to jump due to nerves
 */

class Dive 
{
  public static void main (String args[ ])
  {
    // DECLARE VARIABLES/DATA DICTIONARY
    int tMax; //the maximum number of seconds the diver has to dive
    char[] moves; //reference to a character array showing the sequence of man’s moves
    int num; //the number of seconds taken by the diver to dive
    char again; //the character that will determine whether  the user wants to run another trial

    System.out.println("Diving Chance");
    do
    {
    System.out.println("Please enter the maximum time in seconds to make a dive: ");  
    
    // READ IN GIVENS use our ITI1120 special class for keyboard input 
    tMax = ITI1120.readInt(); //reads in the user's choice
    
    // BODY OF ALGORITHM - Call to the method to solve problem
    moves = dive(tMax); //call to the method
    num = moves.length; //gets the length of the array and removes 1 
    
    // PRINT OUT RESULTS AND MODIFIEDS
    if(moves[num - 1] == 'D') //checks to see if the man dived or not
    {
      System.out.print("The man jumped with the moves ");
      for(int i = 0; i < num; i++) //loop that goes through the array of moves and prints each letter out
      {
      System.out.print(moves[i]);
      }
      System.out.println(" in "+num+" seconds");
    }
    /*else
    {
      System.out.print("The man lost his nerves after the moves ");
      for(int i = 0; i < num; i++) //loop that goes through the array of moves and prints each letter out
      {
      System.out.print(moves[i]);
      }
      System.out.println();
    }*/
    System.out.println("Do you wish to make another dive attempt? (y/n): ");
    again = ITI1120.readChar(); //reads in user's input for starting another run
    if(again == 'n')
    {
      System.out.println("Program terminated!");
    }
    }while(again == 'y');
  }
  
  // Problem Solving Method
  // Description: Determines if the man dives or not
  // Parameters (GIVENS): 
  //    tMax - the maximum number of seconds the diver has to dive
  public static char[] dive(int tMax)
  {  
    // DECLARE VARIABLES/DATA DICTIONARY
    
    // INTERMEDIATES
    int x = 0; //the man's distance in feet
    int index = 0; //the index number for the element in the array
    double p; //the probability of taking a step forward
    double ranNum; //a random number
    
    // RESULT
    char diveRes[] = new char[tMax]; //an array that holds the moves takens, F - foward, B - backward, D - dive
    
    // BODY OF ALGORITHM
    while(index < tMax && x < 10) //keeps going as long we haven't exceeded the maximum time allowed or the man hasn't dived
    {
      ranNum = Math.random(); //creates the random number from 0.0 to 1.0
      p = 1.0 - (x/10.0); //calculates the probability 
      if(ranNum < p)
      {
        x = x + 2;
        diveRes[index] = 'F';
      }
      else
      {
        if(x != 0)
        {
        x = x - 2;
        }
        diveRes[index] = 'B';
      }
      index++;
    }
    if(x == 10) //sets the last element in the array to D if the man dives
    {
      diveRes[index - 1] = 'D';
    }
    // RETURN RESULT
   return diveRes;
  }
  
} // Don't remove this brace bracket!

Where my problem lies is in the main method where I'm checking if moves[num-1] == 'D' because num is getting the length of the full array which has a bunch of garbage at the end so it doesn't know that the last letter really was a D.

We were also told we're not allowed to use strings.

This sounds like a homework problem. Progamming homework questions should be posted in the Engineering, Comp Sci, and Technology homework subforum.

What was the original programming assignment? Have you tried using a simple while loop to find the last letter in your moves array? Have you tried returning a correctly sized array from your dive method? (Right before your return statement, what will the value of index be? Do you see how you can use this to define a new array of the correct size and copy over the letters from diveRes to it, and then return it instead of
diveRes?)
 

Similar threads

Java What is wrong with my Java array and methods code?
  • · Replies 13 ·
Replies
13
Views
4K
C/C++ Question about New syntax of C++
  • · Replies 31 ·
2
Replies
31
Views
3K
Python Shifting an array one postion to the left -- Non Function Vs Function
  • · Replies 17 ·
Replies
17
Views
3K
Why aren't ditto blocks used more often and more transparently?
  • · Replies 13 ·
Replies
13
Views
2K
Polymorphism using pointer to array
  • · Replies 23 ·
Replies
23
Views
2K
Python Transpose of a non-square matrix (without using ndarray.transpose)
  • · Replies 15 ·
Replies
15
Views
5K
C/C++ I cannot get the size of the array after passing it to a function in C++
  • · Replies 20 ·
Replies
20
Views
2K
JavaScript Algorithm to return all subarrays of a given array
  • · Replies 8 ·
Replies
8
Views
4K
Finding the "Runner Up" (Second Highest Value)
  • · Replies 29 ·
Replies
29
Views
4K
Question about getline with fstream
  • · Replies 65 ·
3
Replies
65
Views
7K