Recursion - Finding Index Of Substring
Sep 4, 2012
I have to alter my Sentence class to find the index of the substring "sip" in Mississippi but I'm really not sure where to begin. This is what I have...
Sentence.java
public class Sentence {
private boolean outcome;
private String sentence;
public Sentence(String aSentence) {
sentence = aSentence;
[Code] ....
I know that I need to change public boolean find(String t) to public int indexOf(String t) but I'm not sure what to start doing to get the index of "sip".
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Nov 3, 2014
The only problem I have now is getting a method to return the median element of a LinkedList without using loops of any kind or by using a global counter anywhere.
I've pretty easily figured out how to get the index value for the median number (there is some lee way allowed. If the list has an even size, any of the middle values are accepted) but I can't figure out how to print it without loops.
I'm sure I need to make a method that finds an element at the given index value, but I don't know how to do it without loops.
Here's all of my code. Inside is my Assignment3 class I use for testing, StudentList which contains the LinkedList head and other List methods, and StudentNode which is obviously, the Node class. Also I've attached the first test1.txt file as well.
import java.io.FileNotFoundException;
import java.util.*;
public class Assignment3 {
public static void main (String []args){
StudentList<StudentNode> myList = new StudentList<StudentNode>();
[Code] .....
I tried making a method that basically counts up the list recursively then a second method that counts down recursively and is supposed to stop once it hits the middle number, then print that node.
Attached File(s) : test1.txt (106bytes)
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Jan 29, 2014
int[] a = new int[7];
a[0] = 0;
a[1] = 10;
a[2] = 256;
a[3] = 57;
a[4] = 33;
a[5] = -154;
a[6] = 168;
[code]....
What program needs to find is the most biggest number. It does the job, but another task of the program is to find the index of that number . The second loop should do just that, but for some reason, as the loop goes further, it passes through the if statement even though answer "a[i]" is not equal to "answer". The idea is that if a[i] and answer are equal, the "i" should represent the index number.
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Oct 2, 2014
I have a JSF application with this code in the xhtml page:
<h:selectOneListbox id="selectProduct" size="10" style="width:10em; font-family:monospace" value="#{mybean.product}">
<f:selectItems value="#{mybean.products}" />
</h:selectOneListbox>
and the corresponding snippets of the Java code are:
// Class member variables
// ...
private String product;
private ArrayList<String> productValues;
private ArrayList<String> productLabels;
private SelectItem[] products;
// ... Various properties etc.
public String getLocation() { // Displayed on a page
[code]....
Most of this works correctly using only ArrayList SelectItem products without the two ArrayList and the separate SelectItem[], and the values and labels are put directly into products here. The menu works and I can select an item. However, I am unable to find the correct method for finding the index in the submit method,namely:
public void submit(ActionEvent e) {
showProduct = true;
prodNum = products.indexOf(product); // --- Here is the problem!
updateProduct();
}
which has not been changed here. In spite of trying out various ideas, prodNum always returns with -1, which means it cannot find the index of the selected product, where product is a String. Everything else seems to work correctly, and products.get(prodNum).getLabel() works if I manually give prodNum a valid index, but because it's -1 it fails.
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Apr 23, 2014
I'm trying to use regex to find a word containing the substring "cat." I'm not sure why this isn't working?
String match = "^ cat$";
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Jun 13, 2014
I have one column "category" which contain data like
`"Failed extract of third-party root list from auto update cab at: [URL] with error: The data is invalid."`
I need to select url part in between `" < > "` sign of category column.
how to do this usign regex?
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Mar 22, 2014
(Check substrings) You can check whether a string is a substring of another string by using the indexOf method in the String class. Write your own method for this function. Write a program that prompts the user to enter two strings, and checks whether the first string is a substring of the second.
What the function should return
public class Ex2 {
public static void main(String[] args) {
System.out.println("Input the first string:");
Scanner input = new Scanner(System.in);
String firstString = input.nextLine();
System.out.println("Input the second string:");
String secondString = input.nextLine();
check(firstString,secondString);
[Code] ....
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Apr 22, 2014
Why isn't it working?
Java Code:
if ((line.substring(i,i+2)) == "go")
break; mh_sh_highlight_all('java');
I printed this to check if substring works fine, used this:
Java Code: System.out.println(line.substring(i,i+2) + " : "+ length); mh_sh_highlight_all('java');
So, output:
Er : 1
ra : 2
ag : 3
go : 4
on : 5
n' : 6
'> : 7
Line:
String line = "Eragon'>";
Shouldn't it break loop after printing "go : 4"?
line.substring(i,i+2) prints go here. But if doesn't work.
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Mar 20, 2015
Write a program that reads number between 1,000 and 999,999 from the user and prints it without a comma separating the thousands. Read the input as string. Find the length of the string and use the substring to break it into two pieces. Do not include the comma. You can then concatenate using the + symbol to reassemble without the comma. For example if the number is 123,456. First would equal 123 and second would equal 456. noCommaNumber - 123456.
I do not think it is required to only allow numbers in that range in the code. My question is how to get the first half of the number before the comma in a string to make the last line work. What I think is not doing what I need is the line String first = numberIn.substring(numberIn.indexOf(",", 0)); This is just the last thing I tried.Getting the second half is done using IndexLastOf method in the substring class javaforumquest.jpg
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Sep 10, 2014
Why does the substring method subtract an extra 1?
For example:
myString = "Programming and Problem Solving";
myString.substring(0, 7) would be "Program" instead of "Program".
It's not explained in the book I'm reading and didn't see it online.
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Dec 29, 2014
I am trying for a logic that i have some emp ids as a string seperated by commas and i need the substring of emp ids as below. splitting the string as below.
public static void main(String args[]) {
String empId = "1,2,3,4,5,6,7,8,9,10";
int i;
int count = 9;
for (i = 0; i <= count; i = i + 3) {
System.out.println("Emp IDs are : " +empId);
}}
Result is:
Emp IDs are : 1,2,3,4,5,6,7,8,9,10
Emp IDs are : 1,2,3,4,5,6,7,8,9,10
Emp IDs are : 1,2,3,4,5,6,7,8,9,10
Emp IDs are : 1,2,3,4,5,6,7,8,9,10
But I want the result like:
Emp IDs are : 1,2,3
Emp IDs are : 4,5,6
Emp IDs are : 7,8,9
Emp IDs are : 10
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Jul 16, 2014
I'm still working with the singlylinkedlist data structure and trying to return a string of individual characters stored in each node. ( head--('J')---('A')---('V')---('A')---tail ) Hopefully this beautifully executed depiction to the left will clarify.
This is what I came up with after designing the algorithm w/ pen and paper. I know that I'm not accounting for the OutOfBound errors, an empty list, or an index < 0.... I will get to that.
Right now, I'm not sure why my assignment to the character array, ' chars[i] = cursor.getLink(getElement()); ' , is not working. The two methods getLink and getElement, type Node and T, respectively, exist in my Node class which is a private nested class in MySLList. Why would I be getting the following error: "The method getElement() is undefined for the type StringX" ? Is this a good design and implementation of the substring method?
public String substring(int index) {
char[] chars = new char[(getSize() - index)]; //getSize() defines the size of list in MySLList
Node cursor = null;
//Set the cursor to the node = index
if(cursor == head) {
[Code] ....
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Jun 18, 2014
Need code logic or regex to get substring between two different delimiters and then parse it into Integer array.
My Input String is : Transmitter#MSE14_REC_FTP40 #138^TPPurgeUility_test #103^YUG_Trans #57^
Output (ie. substring between "#" and "^")
138
103
57
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Apr 29, 2014
I am trying to make a game, for some reason i have begun to get a java.lang.StackOverflowError.
I am not exactly sure how i can fix it. only removing line 14 from infopannel1 (and everything that used that class.) seems to work. im not sure what else i can do to fix it. or why its resulting in stack overflow for that matter.
I am putting in a link for the files i wrote this using bluej (several classes have no relevance, errorv2, demonstration, folderreadertest, ReadWithScanner, saveloadtest, menutest,rannum, and menutestTester. are all irrelivent to my problem.)
[URL] .....
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Dec 13, 2014
how does recursion works, I don't understand why it prints al numbers going up again?This is the code
void print2(int n){
if (n<0){
out.printf(" %d",-1);
return;
}
out.printf(" %d", n);
print2(n-1)
out.printf(" %d", n);
}
this should be the output if n is 6: 6 5 4 3 2 1 0 -1 0 1 2 3 4 5 6.
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Mar 25, 2015
How to add the sum of an array with a recursion, but I don't understand how to use recursion. I just understand that it calls back the method. I am nearly done with the code.
import java.util.Scanner;
class Question1{
public static void main(String[]args){
Scanner s = new Scanner(System.in);
int size, sum;
System.out.println("Please input how many numbers will be used");
size=s.nextInt();
[Code] .....
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Aug 6, 2014
public void myFunc(MyNode n, ArrayList<MyNode> path) {
boolean hasChildren = false;
path.add(n);
int index = path.indexOf(n);
ArrayList<MyNode> statefulPath = new ArrayList<MyNode>();
[Code] ....
I have similar code that I stepped through in a debugger. After running the code I found that it built the desired tree, in this case a root node H with left child L and right child P. I want list of lists to contain all paths from root to leaf. I expected [H, L] and [H, P]. I discovered that statefulPath is not stateful; after a recursive stack frame pops, statefulPath still contains n! But that stack frame just popped! I expected to see statefulPath be [H] in the debugger and it was [H, L]! So I later have a list [H,L,P] which I don't want. How do I make the statefulPath list I want for my algorithm?
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Mar 22, 2015
I have a question related to the code below, that I do not understand. The aim is to count all files and subdirectories in an ArrayList full of files and subdirectories. So I have to count every file and every subdirectory.
The code concerning counting files is clear to me - every time d is of the type file I have to increment n by one. However I thought that I have to do the same thing in case d is a directory, so I would have written the same code for directories.
So what does "n += ((Directory) d).countAllFiles();" mean? In my understanding the method countAllFiles() is applied again on the object Directory ( as Directory is the class that contains this method), but how is n incremented by this? I thought n should be incremented by one as we did with files.
public int countAllFiles() {
int n = 0;
for(SystemFile d : content) {
if(d instanceof File) {
n++;
[Code] ....
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Jun 5, 2014
How the recursion works. I tried to figure out writing down low, mid, high at each recursive call. But I seem to be making a mistake somehow. I don't understand where the values are returned to in
if(leftmax>rightmax){
return leftmax;}
else
return rightmax;
Here's the code:
public class Maximum{
public static int max(int[] a,int low,int high){
int mid,leftmax,rightmax;
if(low==high)
return a[low];
[Code] ....
firstly leftmax=max(a,0,4)
Then what is the next line executed?Is it rightmax=max(a,5,8).
After this is it leftmax=max(a,5,6)
rightmax=max(a,7,8)
I tried to understand what these recursion calls by writing them down.But I somehow make a mistake.
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Oct 20, 2014
I just started studying recursion and I wanted to know how to create a palindrome number going up from 1 to n then back to 1 like this: "12345...n...54321".
I've done one going downwards and then upwards like this: "n...4321234...n".
Here's my code:
Java Code: import java.util.*;
public class PalindromeTest
{
public static void downPalindrome(int n)
[Code].....
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Jul 16, 2014
The program I'm working on is supposed to read input from a file and using recursion, print the pattern of asterisks for each value until the value is either < 0 or > 25.For example, if the value was 4, the pattern would look like this
*
* *
* * *
* * * *
* * *
* *
*
The values are stored in a file entitled prog3.dat which looks like this
4
3
15
26
0
I've never used recursion before and haven't been able to find anything showing how it would work with this particular type of problem.Here is what I've been able to come up with so far, but I'm having problems still which I will show following the code.
import java.util.Scanner;
import java.io.*;
public class Program3 {
public static void main(String[] args) throws Exception {
int num = 0;
java.io.File file = new java.io.File("../instr/prog3.dat");
Scanner fin = new Scanner(file);
[code]...
It appears to be reading the file correctly, but is only printing the top half of the pattern. Also, like I said, I'm not very familiar with recursion, so am not sure if this is actually recursion?
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Jul 16, 2014
The program I'm working on is supposed to read input from a file and using recursion, print the pattern of asterisks for each value until the value is either < 0 or > 25. For example, if the value was 4, the pattern would look like this
*
* *
* * *
* * * *
* * *
* *
*
The values are stored in a file entitled prog3.dat which looks like this
4
3
15
26
0
I've never used recursion before and haven't been able to find anything showing how it would work with this particular type of problem. Here is what I've been able to come up with so far, but I'm having problems still which I will show following the code.
import java.util.Scanner;
import java.io.*;
public class Program3 {
public static void main(String[] args) throws Exception {
int num = 0;
java.io.File file = new java.io.File("../instr/prog3.dat");
Scanner fin = new Scanner(file);
[Code] ....
Output:
Please enter an integer
*
* *
* * *
* * * *
Please enter an integer
*
* *
* * *
Please enter an integer
*
* *
* * *
* * * *
* * * * *
* * * * * *
* * * * * * *
* * * * * * * *
* * * * * * * * *
* * * * * * * * * *
* * * * * * * * * * *
* * * * * * * * * * * *
* * * * * * * * * * * * *
* * * * * * * * * * * * * *
* * * * * * * * * * * * * * *
Please enter an integer
Please enter an integer
As you can see, I don't know how to make it print the pattern like in the example and am honestly not even sure if this is recursion since I've never actually worked with recursion before.
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Apr 26, 2015
I was asked to create a word pyramid program using recursion. I understand the concept of recursion (i.e. a method calling itself with the problem it is solving getting simpler and simpler each time) but I am having issues writing the program. Here is my code:
public static void main(String[] args) {
//This program will create a word pyramid by using a recursive algorithm.
//For example, the output of "DOGGY" should be:
//DOGGY
//OGG
//G
//This program will also use a recursive algorithm to accomplish this.
String userWord = JOptionPane.showInputDialog(null, "Hello and welcome to the Word Pyramid program."
[Code] .....
So, if I input HORSE the output should be:
HORSE
ORS
R
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Nov 6, 2014
We are supposed to create a MergeSort method without the using recursion. Most of the code is already completed, the only thing that I believe I need are two for loops (an inner and an outter) that will make calls to the merge method. I need implementing the sort method of the merge sort algorithm without recursion, where the length of the array is a power of 2. Keep merging adjacent regions whose size is a power of 2. For ex: lengths will be 1, 2, 4, 8, 16,.
public class MergeSorter {
public static void sort(int[] a) {
//for(int i = 1; i <= a.length; i++) the parameters for the for loop are wrong.
{
merge(0,0,1,a);
merge(1,1,2,a);
merge(2,2,3,a);
[Code]...
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Nov 26, 2014
Here is what I have so far:
/**
* This class encapsulates a simple dice game. The number of dice and number of sides on those dice are given by instance variables. The outcomes ArrayList holds a list of all possible outcomes of throwing that number of dice with that number of sides.
*
* If there were 2 dice, each with 6 sides, then possible outcomes would include 1 1, 1 2, 1 3, 1 4, 1 5, 1 6, 2 1, 2 2, 2 3, and so on.
*
* Your task is to complete the methods that calculate the possible outcomes. One method calculates outcomes allowing for repeated numbers. One method calculates the outcomes of a fictional dice game where repeated numbers cannot occur.
*
* You must use recursion. This is a variation on the permutations problem from the book.
*/
public class Dice
{
private static int numberOfSides;
private static int numberOfDice;
public ArrayList<String> outcomes;
[code]...
I manage to calculate the numberOfOutcomes correctly, but then get a nullPointerException. Also, is there a way that I can use getNumberOf Outcomes without making it static? The testing code that the teacher provided is using it in another class and if I make it static, then it doesn't work in that file.
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Feb 26, 2014
I have this method
Java Code:
public static int[] oddNums(int n){
} mh_sh_highlight_all('java');
When a number is passed in, this method returns an array of odd numbers the amount of the number passed in.
So
Ex: Class.oddNums(5) would return [ 1, 3, 5, 7, 9 ]
Class.oddNums(2) would return [ 1, 3]
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