I'm stuck on how to write a delete method for a menu (object orientation) program I am writing. The menu gives the user the option to delete the last name entered on the program. I'm completely stuck on this part! Would be greatly appreciated if you guys/gals could show me a simple delete method!
Many Thanks!
This is my code so far for Adding a Name:
public static int addOne(String theArray[], int location, String theName, int noofvalues)
{
int step;
if(noofvalues == 0)
{
theArray[0] = theName;
noofvalues++;
}
else
{
for(step = noofvalues - 1; step >= location; step--)
{
theArray[step + 1] = theArray[step];
}
theArray[location] = theName;
noofvalues++;
}
return noofvalues;
}
Since it looks like homework, I won't provide any code at all (otherwise, I would solve the homework and you won't learn anything), only ideas an possibly an algorithm to do it.
Store the last name inserted by the user in a variable. Let's say, this variable is lastInsertedName.
Go through all the elements in your array and search this String in it. When you find lastInsertedName in the array, store the index in a variable, let's say indexFound and stop the loop.
If indexFound is greater or equals than 0:
Move all the elements starting at indexFound in the array one position back.
Decrease the variable that acts as the size of your array.
Use List:
public static int addOne(List names, int location, String theName, int noofvalues)
{
names.add(location, theName);
return names.size();
}
public static void deleteOne(List names, int location){
names.remove(location);
}
Related
public static int score(int[][] array, int win, int turn) {
int score = 0;
if (GamePrinciples.gameEnd(array, win)) {
if (GamePrinciples.draw(array)) {
score = 0;
} else if (GamePrinciples.winningBoard(array, win)[0] == 1) {
score = 1;
} else {
score = -1;
}
} else {
for (int[][] i : children(array, win, turn)) {
score += score(i, win, GamePrinciples.nextPlayer(turn));
}
}
return score;
}
briefly this program is part of my minimax algorithm. So the problem is that I get a stack over flow. Where am I going wrong?
if an array is in ending mode then if it is a draw it gives a score of zero if player one wins then a score of one and if player two wins it gives a score of two.
if the array is however not in the ending state we get the children of the array (immediate children that is the boards that result from the current board with only one move). The score of the board will be the sum of the score of each of its children. The logic seems okay and the other methods such as children, nextPlayer, winningBoard, draw all work fine with testing. So I am guessing there is problem with this kind of recursive implementation. Can anyone help? Thanks in advance
Your code seems wrong in the loop:
for (int[][] i : children(array, win, turn)) {
I haven’t tested, but you should call the method children() outside the for.
By calling the method within the for clause, you are always returning the initial array instead of iterating through it.
So try putting the children() method return to a variable and iterate through this variable.
Something like:
… c = children(…)
for(int[][] i : c) {
…
so i want to add an element at the top of the array, it works for the first value i insert but if i insert another the one it doesn't get saved to the array. any help would be much appreciated ,thanks in advance.
this is my push function
private static final int STACK_SIZE = 10;
private double [] stack;
protected int top;
public ArrayStack() {
stack = new double[STACK_SIZE];
top = -1;// stack is empty
}
#Override
public void push (double p) throws DataStructureException {
if (!isFull()) {
top++;
stack[top] = p;
}
else
System.err.println( "Stack is full: cannot push " + p );
}
That's because in your condition here
if (!isFull())
{
top++;
stack[top] = p;
}
you increment the index where you're going to add the next element, not the actual position of the element. Since top value is 1 on the second call, the element will be added to stack[1].
I recommend you take a look at some other data structures. Lists for example have a method to add an element to the start of a list which would solve your issue:
list.add(0,p)
Another alternative is using Deque which also has a method to insert at the beginning
https://docs.oracle.com/javase/7/docs/api/java/util/Deque.html
you were increasing the top count before adding , so instead use post increment as index
if (!isFull()) {
if(top==-1){top++};
stack[top++] = p;
}
This is the problem:
You have maps of parts of the space station, each starting at a prison exit and ending at the door to an escape pod. The map is represented as a matrix of 0s and 1s, where 0s are passable space and 1s are impassable walls. The door out of the prison is at the top left (0,0) and the door into an escape pod is at the bottom right (w-1,h-1).
Write a function answer(map) that generates the length of the shortest path from the prison door to the escape pod, where you are allowed to remove one wall as part of your remodeling plans. The path length is the total number of nodes you pass through, counting both the entrance and exit nodes. The starting and ending positions are always passable (0). The map will always be solvable, though you may or may not need to remove a wall. The height and width of the map can be from 2 to 20. Moves can only be made in cardinal directions; no diagonal moves are allowed.
To Summarize the problem: It is a simple rat in a maze problem with rat starting at (0,0) in matrix and should reach (w-1,h-1). Maze is a matrix of 0s and 1s. 0 means path and 1 means wall.You have the ability to remove one wall(change it from 0 to 1). Find the shortest path.
I've solved the problem but 3 of 5 testcases fail and I don't know what those test cases are. and I'm unable to figure out why. Any help would be greatly appreciated.Thanks in Advance. Here is my code:
import java.util.*;
class Maze{//Each cell in matrix will be this object
Maze(int i,int j){
this.flag=false;
this.distance=0;
this.x=i;
this.y=j;
}
boolean flag;
int distance;
int x;
int y;
}
class Google4_v2{
public static boolean isPresent(int x,int y,int r,int c)
{
if((x>=0&&x<r)&&(y>=0&&y<c))
return true;
else
return false;
}
public static int solveMaze(int[][] m,int x,int y,int loop)
{
int r=m.length;
int c=m[0].length;
int result=r*c;
int min=r*c;
Maze[][] maze=new Maze[r][c];//Array of objects
for(int i=0;i<r;i++)
{
for(int j=0;j<c;j++)
{
maze[i][j]=new Maze(i,j);
}
}
Queue<Maze> q=new LinkedList<Maze>();
Maze start=maze[x][y];
Maze[][] spare=new Maze[r][c];
q.add(start);//Adding source to queue
int i=start.x,j=start.y;
while(!q.isEmpty())
{
Maze temp=q.remove();
i=temp.x;j=temp.y;
int d=temp.distance;//distance of a cell from source
if(i==r-1 &&j==c-1)
{
result=maze[i][j].distance+1;
break;
}
maze[i][j].flag=true;
if(isPresent(i+1,j,r,c)&&maze[i+1][j].flag!=true)//check down of current cell
{
if(m[i+1][j]==0)//if there is path, add it to queue
{
maze[i+1][j].distance+=1+d;
q.add(maze[i+1][j]);
}
if(m[i+1][j]==1 && maze[i+1][j].flag==false && loop==0)//if there is no path, see if breaking the wall gives a path.
{
int test=solveMaze(m,i+1,j,1);
if(test>0)
{
test+=d+1;
min=(test<min)?test:min;
}
maze[i+1][j].flag=true;
}
}
if(isPresent(i,j+1,r,c)&&maze[i][j+1].flag!=true)//check right of current cell
{
if(m[i][j+1]==0)
{
maze[i][j+1].distance+=1+d;
q.add(maze[i][j+1]);
}
if(m[i][j+1]==1 && maze[i][j+1].flag==false && loop==0)
{
int test=solveMaze(m,i,j+1,1);
if(test>0)
{
test+=d+1;
min=(test<min)?test:min;
}
maze[i][j+1].flag=true;
}
}
if(isPresent(i-1,j,r,c)&&maze[i-1][j].flag!=true)//check up of current cell
{
if(m[i-1][j]==0)
{
maze[i-1][j].distance+=1+d;
q.add(maze[i-1][j]);
}
if(m[i-1][j]==1 && maze[i-1][j].flag==false && loop==0)
{
int test=solveMaze(m,i-1,j,1);
if(test>0)
{
test+=d+1;
min=(test<min)?test:min;
}
maze[i-1][j].flag=true;
}
}
if(isPresent(i,j-1,r,c)&&maze[i][j-1].flag!=true)//check left of current cell
{
if(m[i][j-1]==0)
{
maze[i][j-1].distance+=1+d;
q.add(maze[i][j-1]);
}
if(m[i][j-1]==1 && maze[i][j-1].flag==false && loop==0)
{
int test=solveMaze(m,i,j-1,1);
if(test>0)
{
test+=d+1;
min=(test<min)?test:min;
}
maze[i][j-1].flag=true;
}
}
}
return ((result<min)?result:min);
}
public static int answer(int[][] m)
{
int count;
int r=m.length;
int c=m[0].length;
count=solveMaze(m,0,0,0);
return count;
}
public static void main(String[] args)
{
Scanner sc=new Scanner(System.in);
System.out.println("enter row size ");
int m=sc.nextInt();
System.out.println("enter column size ");
int n=sc.nextInt();
int[][] maze=new int[m][n];
System.out.println("Please enter values for maze");
for(int i=0;i<m;i++)
{
for(int j=0;j<n;j++)
{
maze[i][j]=sc.nextInt();
}
}
int d=answer(maze);
System.out.println("The maze can be solved in "+d+" steps");
}
}
Found the problem. maze[i][j].flag=true; needs to be put as soon as the cell is visited, inside the if(m[i+1][j]==0) condition. Otherwise, the distance for same cell can be added by more than one cells
Unfortunately it's quite hard to help you because your code is very difficult to read. The variables are generally single characters which makes it impossible to know what they are supposed to represent. Debugging it would be more help than most of us are willing to give :-)
I suggest you go about debugging your code as follows:
Split your solveMaze method into a number of smaller methods that each perform much simpler functions. For example, you have very similar code repeated 4 times for each direction. Work to get that code in a single method which can be called 4 times. Move your code to create the array into a new method. Basically each method should do one simple thing. This approach makes it much easier to find problems when they arise.
Write unit tests to ensure each of those methods do exactly what you expect before attempting to calculate the answer for entire mazes.
Once all the methods are working correctly, generate some mazes starting from very simple cases to very complex cases.
When a case fails, use an interactive debugger to walk through your code and see where it is going wrong.
Good luck.
As title says I need to do the following. But I somehow am getting the wrong answer, perhaps something with the loops is wrong?
And here's what I have coded so far, but it seems to be giving me the wrong results. Any ideas, help, tips, fixes?
import java.util.ArrayList;
public class pro1
{
private String lettersLeft;
private ArrayList<String> subsets;
public pro1(String input)
{
lettersLeft = input;
subsets = new ArrayList<String>();
}
public void createSubsets()
{
if(lettersLeft.length() == 1)
{
subsets.add(lettersLeft);
}
else
{
String removed = lettersLeft.substring(0,1);
lettersLeft = lettersLeft.substring(1);
createSubsets();
for (int i = 0; i <= lettersLeft.length(); i++)
{
String temp = removed + subsets.get(i);
subsets.add(temp);
}
subsets.add(removed);
}
}
public void showSubsets()
{
System.out.print(subsets);
}
}
My test class is here:
public class pro1
{
public static void main(String[] args)
{
pro1s = new pro1("abba");
s.createSubsets();
s.showSubsets();
}
}
Try
int numSubsets = (int)java.lang.Math.pow(2,toSubset.length());
for (int i=1;i<numSubsets;i++) {
String subset = "";
for (int j=0;j<toSubset.length();j++) {
if ((i&(1<<j))>0) {
subset = subset+toSubset.substring(j,j+1);
}
}
if (!subsets.contains(subset)) {
subsets.add(subset);
}
}
where toSubset is the string that you wish to subset (String toSubset="abba" in your example) and subsets is the ArrayList to contain the results.
To do this we actually iterate over the power set (the set of all subsets), which has size 2^A where A is the size of the original set (in this case the length of your string).
Each subset can be uniquely identified with a number from 0 to 2^A-1 where the value of the jth bit (0 indexed) indicates if that element is present or not with a 1 indicating presence and 0 indicating absence. Note that the number 0 represents the binary string 00...0 which corresponds to the empty set. Thus we start counting at 1 (your example did not show the empty set as a desired subset).
For each value we build a subset string by looking at each bit position and determining if it is a 1 or 0 using bitwise arithmetic. 1<<j is the integer with a 1 in the jth binary place and i&(i<<j) is the integer with 1's only in the places both integers have a 1 (thus is either 0 or 1 based on if i has a 1 in the jth binary digit). If i has a 1 in the jth binary digit, we append the jth element of the string.
Finally, as you asked for unique subsets, we check if we have already used that subset, if not, we add it to the ArrayList.
It is easy to get your head all turned around when working with recursion. Generally, I suspect your problem is that one of the strings you are storing on the way down the recursion rabbit hole for use on the way back up is a class member variable and that your recursive method is a method of that same class. Try making lettersLeft a local variable in the createSubsets() method. Something like:
public class Problem1
{
private String originalInput;
private ArrayList<String> subsets;
public Problem1(String input)
{
originalInput = input;
subsets = new ArrayList<String>();
}
// This is overloading, not recursion.
public void createSubsets()
{
createSubsets(originalInput);
}
public void createSubsets(String in)
{
if(in.length() == 1)
{
// this is the stopping condition, the bottom of the rabbit hole
subsets.add(in);
}
else
{
String removed = in.substring(0,1);
String lettersLeft = in.substring(1);
// this is the recursive call, and you know the input is getting
// smaller and smaller heading toward the stopping condition
createSubsets(lettersLeft);
// this is the "actual work" which doesn't get performed
// until after the above recursive call returns
for (int i = 0; i <= lettersLeft.length(); i++)
{
// possible "index out of bounds" here if subsets is
// smaller than lettersLeft
String temp = removed + subsets.get(i);
subsets.add(temp);
}
subsets.add(removed);
}
}
Something to remember when you are walking through your code trying to think through how it will run... You have structured your recursive method such that the execution pointer goes all the way down the recursion rabbit hole before doing any "real work", just pulling letters off of the input and pushing them onto the stack. All the "real work" is being done coming back out of the rabbit hole while letters are popping off of the stack. Therefore, the first 'a' in your subsets list is actually the last 'a' in your input string 'abba'. I.E. The first letter that is added to your subsets list is because lettersLeft.length() == 1. (in.length() == 1 in my example). Also, the debugger is your friend. Step-debugging is a great way to validate that your code is actually doing what you expect it to be doing at every step along the way.
I get the error message cannot find symbol, symbol: method books(int[], int) when I try to compile the following code.
For further explanation about what I want the code to do, see below the code.
public class books {
public void main(String[] args) {
int searchValue = 0, index;
int refNum[] = new int[4]; // the array
refNum[0] = 4; //numbers to refer to (aka to find)
refNum[1] = 6;
refNum[2] = 10;
refNum[3] = 12;
refNum[4] = 14;
int input = Integer.parseInt(enterValue.getText()); //takes user's input
for (int x = 0; x < refNum.length; x++) {
refNum[x] = input; //Tells refNum value to be
}
searchValue = input;
index = books(refNum, searchValue); //"books" is underlined
if (index != -1) {
binarySearchField.setText("We found: " + index);
} else {
binarySearchField.setText("Sorry! Not Found!");
}
public static Boolean binarySearch(String [] refNum, int left, int right, String search){
//Boolean code for later
}
This program uses binary search to find values stored in array after user inputs number, if they match then the item is successfully found. User inputs desired number in 'enterNumber' which is a TextField. Now in my code )which I'm 78% sure will work if it wasn't for this one little thing) there is an all important that is underlined which shouldn't be, (I've commented beside the line to show)
Now I had thought I was suppose to put the class name there, but apparently since it is underlined that is not the case. Any ideas on what I should be putting there in it's place?
And I apologize for the question may be a bit misleading on what I'm really asking, I just wasn't sure how to word the question.
The line
index = books(refNum, searchValue);
seems to be underlined because you have no method called books that takes an int[] and an int as arguments in your books class definition.
Now I had thought I was suppose to put the class name there Why do you assume you have to put the class name there? Figure out what you are trying to do with this code and then you will understand what goes in that line (at least in pseudocode).
Also it seems like you have a method declared directly inside another method. That is not legal in java. If this is not the case, please show us correct code.
books is your class's name..that might be the reason you are getting this error. You can't call constructor like a method. Change class's name to Books or something else..or change method's name