Hi i was given a task in Processing and the question is this "You are asked to store a small telephone contact list that can hold ten names and ten matching telephone numbers. show how you would write a function that takes a name, a telephone number and index as parameters and sets the array(s) at the index position to the values given. Include in your answer code that checks the index given is a valid position in your array(s)."
I've come up with the code below
String[] names = new String[10];
int[] numbers = new int[10];
String[] contact = new String[10];
void setup() {
names[0] = "p1";
names[1] = "p2";
names[2] = "p3";
names[3] = "p4";
names[4] = "p5";
names[5] = "p6";
names[6] = "p7";
names[7] = "p8";
names[8] = "p9";
names[9] = "p10";
numbers[0] = 1;
numbers[1] = 2;
numbers[2] = 3;
numbers[3] = 4;
numbers[4] = 5;
numbers[5] = 6;
numbers[6] = 7;
numbers[7] = 8;
numbers[8] = 9;
numbers[9] = 10;
for (int i=0; i<10; i++) {
contact[i] = "Name:"+names[i] +" "+ "Number:" + numbers[i]+" ";
println(contact[i]);
}
}
But my teacher's comment to my code were this "So what I expected here was a simple function that took an index, a number and a name as parameters and then filled in the arrays at the index value with the values." I'm quite confused about this question, is void setup not a function? and i really don't know what it means by making index, number and name as parameters. So if anyone can point out to me thanks!
EDIT: improved code
void setup() {
for (int i=0; i<10; i++){
contactList(i, "aName", 123456789);//default value to all 10 elememnts
}
}
void contactList(int index, String name, int number) {
println (index, "Name:" + name, "Number:" + number);
}
Do you know how to write a function? Hint: you do, you wrote the setup() function! Can you write another function that takes parameters? Start with a simple function that just takes a parameter and prints it out. Work from there.
Here's a little example that takes a String as a parameter and prints it out, which is called from the setup() function:
void setup(){
printMe("hello!");
}
void printMe(String text){
println(text);
}
Recommended reading:
Passing Information to a Method or a Constructor - Java Tutorials
Writing Your Own Functions - Static Void Games Tutorials
Related
I'm trying to make a code that removes all the elements from the array that are equal to a given value. For example an array = [hi, hello, hi, bye] value = hi, it would given an output hello bye
Here's my code:
int count = 0;
for(int i=0; i<stringArr.length;
if(stringArr[i].equals(value)){
count--;
for(int j= i; j<stringArr.length-1; j++){
stringArr[j] = stringArr[j+1];
}
i--;
}
}
Problem is instead of the expected output as: hello bye
It gives an output of:
hello hi bye bye
Try Java stream api:
String value = "hi";
String[] stringArr = new String[] {"hi", "hello", "hi", "bye"};
String[] results = Arrays.stream(stringArr)
.filter(it -> !it.equalsIgnoreCase(value))
.toArray(String[]::new);
The problem is that you are shifting the values left but not decrementing the length of the array in the outer for.
Assign stringArr.length to count and use it in the for.
Trading memory for speed, you could create a new array of the same length and only add in the first occurrence of what you want.
String[] removeEqual(String[]array,String val){
boolean found =false;
String[]out=new String[array.length];
int count=0;
for (int i=0;i<array.length;i++){
if(array[i].equals(val)){
if(!found){
out[count++]=val;
found=true;
}
else out[count++]=val;
}
}
return Arrays.copyOf(out, count);
}
You may like to consider separate functions for separate conditions such as removeLessThan and removeGreaterThan to keep it functionally coherent.
I don't recommend to do any manipulation to the original array, create a new one. Recycling is good for the planet, but may be very harmful in code. So if you want to stick to the Arrays only, then create a new array with and add all elements you want into the new array, but I think you can do better. Your approach is very "C" like, this is Java, you have a lot of better tools, than arrays.
One of them are streams and lambdas like this
#Test
public void example_lambdas() {
String[] array = {"hi", "hello", "hi", "bye"};
String[] result = Arrays.stream(array).filter(element -> !"hi".equals(element)).toArray(String[]::new);
System.out.println(Arrays.toString(result));
}
Another option is to use list
#Test
public void example_list() {
String[] array = {"hi", "hello", "hi", "bye"};
List<String> list = new ArrayList<>(Arrays.asList(array));
Set<String> toBeRemoved = Collections.singleton("hi");
list.removeAll(toBeRemoved);
String[] result = list.toArray(new String[0]);
System.out.println(Arrays.toString(result));
}
An array has a fixed size that cannot be changed. Hence your result cannot be a two element array when you start with a four element array. If you want the result to be a two element array, then you will need to create a second array. If, however, you want the result to stay in the original array, then I suggest setting the excess array elements to null. The following code demonstrates.
String[] stringArr = {"hi", "hello", "hi", "bye"};
String condition = "==";
String value = "hi";
int count = stringArr.length;
for (int i = 0; i < count; i++) {
if (condition.equals("==")) {
if (stringArr[i].equals(value)) {
count--;
for (int j = i; j < stringArr.length - 1; j++) {
stringArr[j] = stringArr[j + 1];
}
stringArr[stringArr.length - 1] = null;
}
}
}
System.out.println(java.util.Arrays.toString(stringArr));
The above code prints the following:
[hello, bye, null, null]
EDIT
As requested, below code creates a new array that only contains the requested elements, i.e. the ones that were not removed from the original array.
String[] stringArr = {"hi", "hello", "hi", "bye"};
String condition = "==";
String value = "hi";
String[] temp = new String[stringArr.length];
int count = 0;
for (int i = 0; i < stringArr.length; i++) {
if (condition.equals("==")) {
if (!stringArr[i].equals(value)) {
temp[count++] = stringArr[i];
}
}
}
String[] result = new String[count];
for (int i = 0; i < count; i++) {
result[i] = temp[i];
}
System.out.println(Arrays.toString(result));
The above code prints the following:
[hello, bye]
In other words, result is a two element array.
Note that I assume that you only want to do array manipulation and you don't want to use classes in the JDK that most of the other answers have used.
I have a problem with my code below:
public class stringToChar {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
char[] sCharArr;
String[] odd = new String[n];
String[] even = new String[n];
for(int i = 0; i < n; i++) {
sCharArr = in.next().toCharArray();
for(int j = 0; j < sCharArr.length; j++) {
if(j % 2 == 0)
even[i] += sCharArr[j];
else
odd[i] += sCharArr[j];
}
}
for(int i = 0; i < n; i++) {
System.out.println(even[i] + " " + odd[i]);
}
}
}
My issue is on the output it has a Null in the result. Here is a sample scenario:
2
John
Cena
Answer should be:
Jh on
Cn ea
But my code answer is:
NullJh Nullon
NullCn Nullea
Your problem is that the new arrays are initialized with all null Strings. Then your code is not assigning values to all array elements, but just to some of them!
Finally you print your array, and surprise, those values that were null and that have not been changed - are still null (and when you print a null string ... it prints "null" [ yes, null, not Null; you got a little mistake there in your output example ]
You see, you iterate from 0 to the length of your two arrays. And if the number is even, you put a value in the even[i]; and if the value is odd, it goes to odd[i]. Lets take even - in that case, odd[i] simply stays null!
One way to fix that:
List<String> even = new ArrayList<>();
List<String> odd = new ArrayList<>();
And now, instead of setting a certain index in even/odd; you simply do:
even.add(some new value);
and to add those single characters:
even.add(new String(sCharArr));
Doing so, even and odd will (in the end) contain exactly the values that you added to each list; but no "residual" nulls. For the record: the way how you split up strings, to then pull them back into a String array isn't exactly the most simple/straight forward way to solve the problem.
But I leave "further" simplifications" as exercise to the user.
I have a string that a user inputs through Console.ReadLine() e.g. "140 150 64 49" (separated only with spaces) and I want to add those numbers to an array. What is the best way to do it. I'm kinda new to programming so I'm a bit lost. Google didn't help either.
When saying you're using Console.ReadLine(), I assume you use C#.
you can use this:
int counter = 0;
int[] array = new int[200]; // choose some size
string s = Console.ReadLine();
int indexOfNextSpace;
while ((indexOfNextSpace = s.IndexOf(' ')) > -1)
{
int num = int.Parse(s.Substring(0, indexOfNextSpace));
array[counter] = num;
counter++;
s = s.Substring(indexOfNextSpace + 1);
}
if you're not sure about valid input, try surrounding with try\catch, or use int.TryParse instead of int.Parse.
You can use this:
List<int> ints = new List<int>();
int num;
int[] result = new int[] { };
string input = Console.ReadLine();
foreach (string str in input.Split(' '))
{
if (int.TryParse(str, out num))
{
ints.Add(num);
}
}
result = ints.ToArray();
foreach (int i in result)
{
Console.WriteLine(i);
}
It uses a List then convert it to array. Note that items are validated, so only ints are added.
This will produce the following output:
123 456 dsf def 1
123
456
1
I currently have a 2D char array size: [5][256].
The array can hold either numbers or letters.
I have been tasked with using the Selection Sort to sort the strings into ascending order.
My idea is to convert each row into ASCII and then sort the values in ascending order then convert back to chars.
Ive implemented a 2D Array Selection sort for another task, however, it doesnt work here as i coded it to work with 2 columns not 256 like here (not sure how to change it).
What i need help with is how do i use the ASCII value for each row and use it in a selection sort.
Been trying to figure this out for hours now, driving me mental.
Any help is appreciated.
Im not necessarily looking for someone to code everything for me, more of a kick in the right direction. Im new to C and not aware of every function C can do.
Here is my current code in full:
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{
char arc5Strings[5][256];
int nCount, nCount2, nCount3, nCount4, nCount5, nCount6, nCount7;
int fMinVal[1][2] = {1,1};
int nMinValPosition;
int nMoves;
int nRow;
int fTemp[1][2] = {1,1};
int fTemp2[1][2] = {1,1};
//input the values
for(nCount=0; nCount < 5; nCount++)
{
printf("Please input string %d/5: ", nCount + 1);
fgets(arc5Strings[nCount], 256, stdin);
}
printf("\n\n");
//print entire array
for(nCount3 = 0; nCount3 < 5; nCount3++)
{
for(nCount4 = 0; arc5Strings[nCount3][nCount4] != '\0'; nCount4++)
{
printf("%d ", arc5Strings[nCount3][nCount4]);
//ASCII values outputted in a line instead of in array format when using %c
}
}
return 0;
}
Old 2D Array selection sort i devised - extracted from code:
//-----------------------------------
//set up the switch
for(nCount5 = 0; nCount5 < 5; nCount5++)
{
fMinVal[0][0] = arc5Strings[nCount5][0]; //min value is row 0 col 1
nMinValPosition = nCount5;
for(nCount6 = nCount5 + 1; nCount6 < 5; nCount6++)
{
if(arc5Strings[nCount6][1] < fMinVal[0][0])
{
fMinVal[0][0] = arc5Strings[nCount6][0];
nMinValPosition = nCount6;
}
/* Perform the switch - actually switch the values */
if(fMinVal[0][0] < arc5Strings[nCount5][0])
{
fTemp[0][1] = arc5Strings[nCount5][1];
fTemp2[0][0] = arc5Strings[nCount5][0];
arc5Strings[nCount5][1] = arc5Strings[nMinValPosition][1];
arc5Strings[nCount5][0] = arc5Strings[nMinValPosition][0];
arc5Strings[nMinValPosition][1] = fTemp[0][1];
arc5Strings[nMinValPosition][0] = fTemp2[0][0];
nMoves++;
}
}
}
//------------------------------
printf("\n\n");
printf("The sorted list, in ascending order, using selection sort, is:\n\n");
for(nCount3 = 0; nCount3 < 5; nCount3++)
{
for(nCount4 = 0; arc5Strings[nCount3][nCount4] != '\0'; nCount4++)
{
printf("%c", arc5Strings[nCount3][nCount4]);
}
}
printf("\n %d moves were made to sort this list\n", nMoves);
EDIT - RESULTS OF GEORGE'S ANSWER:
Input1 = 90
Input2 = 70
Input3 = abc
Input4 = 500
Input5 = 200
Sorted Array Results:
200
90
70
abc
500
You're on the right track. I would implement this as follows:
for(i=0;i<5;i++)
{
indexOfCurrentSmallest = i;
for(j=i;j<5;j++)
{
for(k=0;k<255;k++)
{
if(arc5Strings[j][k] < arc5Strings[indexOfCurrentSmallest][k])
{
//we found a new possible smallest
indexOfCurrentSmallest = j;
break;
}
else if(arc5Strings[j][k] > arc5Strings[indexOfCurrentSmallest][k])
{
//no point in searching further, the one we are looking at is already larger than the one we found.
break;
}
}
}
//here, we have found the actual smallest, let's do a swap
for(q=0;q<255;q++)
{
temp = arc5Strings[i][q];
arc5Strings[i][q] = arc5Strings[indexOfCurrentSmallest][q];
arc5Strings[indexOfCurrentSmallest][q] = temp;
}
}
I haven't tested this code, but it should be roughly what you're looking for. Basically, it compares ASCII values starting at the left, until it finds a difference, and stores the index for later swapping after comparing all 5 strings.
EDIT I've now tested the code above, and it works now.
First find each string length
int length[5];
for(i = 0, i < 5, i++){
length[i] = strlen(arc5Strings[i]);
}
Sort the lengths. Those with the same, compare the value of the first letter.
Thats it.
valter
I think it is basically an easy problem, but I'm stuck. My brain is blocked by this problem, so I hope you can help me.
I have 2 to N arrays of integers, like
{1,2,3,4,5}
{1,2,3,4,5,6}
{1,3,5}
.....
Now i want to have a list containing arrays of int[N] with every posibillity like
{1,1,1}
{1,1,3}
{1,1,5}
{1,2,1}
....
{1,3,1}
....
{2,1,1}
{2,1,3}
....
{5,6,5}
so there are 6*5*3 (90) elements in it.
Is there a simple algorithm to do it? I think the language didn't matter but I prefer Java.
Thx for the help!
I add a valid answer with the implementation in java for the next guy, who has the same problem. I also do it generic so u can have any CartesianProduct on any Object, not just ints:
public class Product {
#SuppressWarnings("unchecked")
public static <T> List<T[]> getCartesianProduct(T[]... objects){
List<T[]> ret = null;
if (objects != null){
//saves length from first dimension. its the size of T[] of the returned list
int len = objects.length;
//saves all lengthes from second dimension
int[] lenghtes = new int[len];
// arrayIndex
int array = 0;
// saves the sum of returned T[]'s
int lenSum = 1;
for (T[] t: objects){
lenSum *= t.length;
lenghtes[array++] = t.length;
}
//initalize the List with the correct lenght to avoid internal array-copies
ret = new ArrayList<T[]>(lenSum);
//reusable class for instatiation of T[]
Class<T> clazz = (Class<T>) objects[0][0].getClass();
T[] tArray;
//values stores arrayIndexes to get correct values from objects
int[] values = new int[len];
for (int i = 0; i < lenSum; i++){
tArray = (T[])Array.newInstance(clazz, len);
for (int j = 0; j < len; j++){
tArray[j] = objects[j][values[j]];
}
ret.add(tArray);
//value counting:
//increment first value
values[0]++;
for (int v = 0; v < len; v++){
//check if values[v] doesn't exceed array length
if (values[v] == lenghtes[v]){
//set it to null and increment the next one, if not the last
values[v] = 0;
if (v+1 < len){
values[v+1]++;
}
}
}
}
}
return ret;
}
}
As i understand what you want, you need to get all permutations.
Use recursive algorithm, detailed here.
As I see this should work fine:
concatMap (λa -> concatMap (λb -> concatMap (λc -> (a,b,c)) L3) L2) L1
where concatMap(called SelectMany in C#) is defined as
concatMap f l = concat (map f l).
and map maps a function over a list
and concat(sometimes called flatten) takes a List of List and turns it into a flat List