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Thread: Frog jumping code (AP comp science help!)

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    Question Frog jumping code (AP comp science help!)

    My computer science teacher told my class to write a code where a frog jumps a staircase to eat a fly. The frog can only jump 3 stairs at once and the frog must jump any number of stairs input. The program must compute the number of possible ways the frog can get to the top of the staircase and also spit out the paths it can take. s= # of stairs
    V My code so far has errors in the jumpsPossible method and I really don't understand why can anyone help?
    class frog {
    static int totalPaths=0;
    	public static void jumpsPossible(int i, int s, String path){
    		if (i==s){
    			totalPaths++;
    			System.out.println (path);
    		}
    		if (i<s){
    			jumpsPossible(i+1,s,path+1);
    			jumpsPossible(i+2,s,path+2);
    			jumpsPossible(i+3,s,path+3);
    		}
    	}
    	public static void main (String [] args) {
    		Integer s = Integer.valueOf(args [0]);
    		System.out.println ("Freddie the Frog will now jump" + s + " stairs to catch a fly!");
    		jumpsPossible(0,s,"");
    		System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible + " ways.");
    	}
    }
    Last edited by CompScienceStudent1; September 20th, 2011 at 08:35 PM.


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    Default Re: Frog jumping code (AP comp science help!)

    Can you post the output from the program and add comments to show what it should be.

    Please edit your post and wrap the code in code tags.
    Press the Go Advanced button, select the code and press the #icon.

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    Default Re: Frog jumping code (AP comp science help!)

    the output should show (lets say the input is 5 stairs so. . .)
    Freddie the Frog will now jump 5 stairs to catch a fly!
    12345
    1245
    1345
    1235
    135
    145
    125
    2345
    245
    235
    25
    345
    35
    Freddie can get to the top of the staircase in 13 ways.

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    Default Re: Frog jumping code (AP comp science help!)

    Is that the output from the program?
    Can you copy the console for when you execute the program?
    To copy the contents of the command prompt window:
    Click on Icon in upper left corner
    Select Edit
    Select 'Select All' - The selection will show
    Click in upper left again
    Select Edit and click 'Copy'

    Paste here.

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    Default Re: Frog jumping code (AP comp science help!)

    Please edit your post and wrap the code in code tags.
    Press the Go Advanced button, select the code and press the #icon.

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    Default Re: Frog jumping code (AP comp science help!)

    No that is what should be the output
    when i try to compile i get an error:
    kulbir-sabharwals-imac:Raina kulbirsabharwal$ javac -classpath . frog.java
    frog.java:18: cannot find symbol
    symbol : variable jumpsPossible
    location: class frog
    System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible + " ways.");
    ^
    1 error

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    Default Re: Frog jumping code (AP comp science help!)

    Where is the variable: jumpsPossible defined? The compiler can not find its definition.
    You have a method by that name. Do you another variable with a new name?

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    Default Re: Frog jumping code (AP comp science help!)

    The method jumpsPossible is determining the number of possible combinations and the ways in which the frog can jump, so I am trying to print the results of that method in main. . .

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    Default Re: Frog jumping code (AP comp science help!)

    System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible + " ways.");
    The above is coded as a variable, not a method. A method call ends with ()s like this:
    jumpsPossible(0,s,"");

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    Default Re: Frog jumping code (AP comp science help!)

    but i wrote that o.o so confused x.x i did call the method

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    Default Re: Frog jumping code (AP comp science help!)

    System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible + " ways.");
    Where do you define the variable (red) used in the above println statement?

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    Default Re: Frog jumping code (AP comp science help!)

    but its not a variable I'm trying to call the jumpsPossible method

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    Default Re: Frog jumping code (AP comp science help!)

    A method has () after it. Look at your code again. There are no ()s after the name in this statement:
    System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible + " ways.");
    Without ()s the compiler thinks its a variable. This is NOT a call to a method.

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    Default Re: Frog jumping code (AP comp science help!)

    so if i change jumpsPossible in that line to jumpsPossible (0,s,"")
    this is the error:
    frog.java:18: 'void' type not allowed here
    System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible(0,s,"") + " ways.");

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    Default Re: Frog jumping code (AP comp science help!)

    : 'void' type not allowed here
    That is because the jumpsPossible() method does NOT return any value. It is a void type.

    Where is the number of jumps value stored? Do you have a class variable that has it?

    Should the jumpsPossible() method return a value instead of being void?

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