I dont have any clue how to approach the problem i am facing. We have to print out an array using function.Function as a parameter and using lambas to print out 1. the even and 2. the odd numbers.
final class Main
{
private Main() {}
public static void main(String[] argv)
{
// Fill the array with integer values and print out only
// values of even indices
DataStructure ds = new DataStructure();
ds.printEven();
// Even
ds.print(..);
}
// Odd
ds.print(...);
}
// end of main class
import java.util.Arrays;
import java.util.function.Function;
class DataStructure
{
// Create an array
private final static int SIZE = 15;
private int[] arrayOfInts = new int[SIZE];
int getSize()
{
return SIZE;
}
int[] getInts()
{
return arrayOfInts;
}
DataStructure()
{
// fill the array with ascending integer values
for (int i = 0; i < SIZE; i++)
{
arrayOfInts[i] = i;
}
}
private DataStructureIterator getIterator(IteratorStrategy strategy)
{
return strategy.getIterator(this);
}
void print(IteratorStrategy strategy)
{
DataStructureIterator iterator = getIterator(strategy);
while (iterator.hasNext())
{
System.out.print(iterator.next() + " ");
}
}
void printEven()
{
// Print out values of even indices of the array
DataStructureIterator iterator =
getIterator(newEvenIteratorStrategy());
while (iterator.hasNext())
{
System.out.print(iterator.next() + " ");
}
System.out.println();
}
//this method is still missing - we have to use the given parameters
void print(java.util.function.Function <Integer,Boolean> iterator)
{
}
}
The expected output is for isEven 0 2 4 6 8 10 12 14
and for isOdd 1 3 5 7 9 11 13
The rest of the given class shouldn't be important atleast i think so.
I am searching for solutions or just a hint for hours but I dont find anything useful. Your help is much appreciated and sorry for my english
If you need anything let me know. Btw I am new to stackoverflow so I hope I did everything right
Not sure that I understood what you really wanted but maybe you should have
a look at this link: https://www.boraji.com/java-8-javautilfunctionfunction-example.
It explains how to use the Function interface and gives an example with even and odds number...
In your case, Function<Integer, boolean> means that you are going to receive an Integer as input and that you must return a boolean (I suppose true if even and false if odd).
Hope it helps! ;)
Related
This question already has answers here:
Scramble each digit of the int a and print out the biggest possible integer
(4 answers)
Closed 2 years ago.
For example, if someone inserts 34603, the output would be 64330. I've started this problem already but I can not think of a solution that works. Also, since this is an assignment, my instructor told me that arrays are not allowed. Here is what I have thus far:
public class loops{
loops(){}
public void biggest(int a){
String as = Integer.toString(a);
int index=0;
int asl = as.length();
while(index<asl){
String num1 = as.substring(index);
String num2 = as.substring((index+1));
int con1 = Integer.parseInt(num1);
int con2 = Integer.parseInt(num2);
if(con1<con2){
System.out.println("con2: "+con2);
}
if(con1>con2){
System.out.println("con1: "+con1);
}
System.out.println("added: "+con1+" "+con2);
index++;
}
}
public static void main(String []args){
loops x = new loops();
x.biggest(4583);
}
}
I would appreciate any and all help/hints, for I am truly lost on this one.
It should be reasonably obvious that the largest possible result is obtained by arranging the digits in descending order. One of the easier and more efficient ways of doing that would be with a counting sort, but the usual forms of that involve using arrays or array-equivalents to accumulate the counts.
So standard Counting Sort is out, along with all standard sort routines aimed at rearranging sequences of items. But you can still take your inspiration from Counting Sort. For example, figure out how many 9 digits are in the input, and form a number from that many 9s. Then figure out how many 8s and append them. Then how many 7s, etc. "Appending" digits to a number can be done arithmetically, so the whole procedure can be done without an array or array equivalent, even if we consider Strings to be array equivalents (as we should).
Details are left as the exercise they are intended to be.
I won't answer the question directly for you but suggest some ideas to help you.
you need to sort the integers in place - ie no arrays/no lists.. just iterate over the integer as a string which you're doing correctly, and progressively swap values so that you end up with a sorted numerical value.
thinking of various sort algorithms, quicksort, mergesort, bubble sort, etc. you effectively pick one of these algorithms and try to implement it.
start with the basic examples for integers to sort and iteratively develop your code to successively generate the correct answer... as test cases try:
no number at all... null
then the empty string ""
then a single digit, so a number 0-9
Next two digits both in order, then out of the sort order
then 3 digits in/out of order
Once you've implemented for 3 digits you should be able to generate your solution for any number of digits.
Note: if you use Integer as the input data type, you will be limited to being able to take a maximum integer value of Integer.MAX_VALUE (which isn't that large). Try to treat the input argument as a String and the individual digits as integers for the comparison (which you are already doing), this way you'll be able to process a much larger input.
import java.util.ArrayList;
import java.util.Collections;
public class loops{
loops(){}
public void biggest(int a){
String as = Integer.toString(a);
int index=0;
int index2=1;
int asl = as.length();
ArrayList<Integer> lista = new ArrayList<Integer>();
while(index<asl){
String num1 = as.substring(index,index2);
int con1 = Integer.parseInt(num1);
lista.add(con1);
index++;
index2++;
}
//order list
Collections.sort(lista);
Collections.reverse(lista);
System.out.println(lista);
//concatenate numbers
}
public static void main(String []args){
loops x = new loops();
x.biggest(34603);
}
}
**anything consult back. **
Ok, I came up with this. It's not the prettiest solution, I recognize that, but it DOES work. Have a look:
public class loops{
public int a,b,c,d,e,f,g,h,i,j;
public loops(){}
public void biggest(int a){
String as = Integer.toString(a);
int index=0;
a = 0;
b = 0;
c = 0;
d = 0;
e = 0;
f = 0;
g = 0;
h = 0;
i = 0;
j = 0;
int asl = as.length();
while(index<asl){
String num3 = as.substring(index,(index+1));
int con3 = Integer.parseInt(num3);
if(con3==9){a++;}
if(con3==8){b++;}
if(con3==7){c++;}
if(con3==6){d++;}
if(con3==5){e++;}
if(con3==4){f++;}
if(con3==3){g++;}
if(con3==2){h++;}
if(con3==1){i++;}
if(con3==0){j++;}
index++;
}
for(int z=0;z<a;z++){
System.out.print("9");
}
for(int y=0;y<b;y++){
System.out.print("8");
}
for(int x=0;x<c;x++){
System.out.print("7");
}
for(int w=0;w<d;w++){
System.out.print("6");
}
for(int v=0;v<e;v++){
System.out.print("5");
}
for(int u=0;u<f;u++){
System.out.print("4");
}
for(int t=0;t<g;t++){
System.out.print("3");
}
for(int s=0;s<h;s++){
System.out.print("2");
}
for(int r=0;r<i;r++){
System.out.print("1");
}
for(int q=0;q<j;q++){
System.out.print("0");
}
public static void main(String []args){
loops x = new loops();
x.biggest(45683408);
}
}
If arrays aren't allowed, then I don't think strings should be allowed either:
static void biggest(int n)
{
long counts=0;
for(; n>0; n/=10)
{
counts += 1L<<((n%10)*4);
}
long result=0;
for (long digit=9; digit>=0; --digit)
{
for(long rep=(counts>>(digit*4))&15; rep>0; --rep)
{
result = result*10 + digit;
}
}
System.out.println(result);
}
This question already has answers here:
How do I print my Java object without getting "SomeType#2f92e0f4"?
(13 answers)
What's the simplest way to print a Java array?
(37 answers)
Closed 2 years ago.
I am trying to solve a popular problem on leetcode called two sum on my ide(intellij). I am expecting it to print index of values inside the array but its printing a memory address. I did some searching and found that i need to override to string(), i did the override and its still printing the memory address. what am i doing wrong? If anyone can help me out, i would appreciate it. Thank you. :)
import java.util.HashMap;
import java.util.Map;
public class Main {
#Override
public String toString() {
return super.toString();
}
public static void main(String[] args) {
int arr[]={2,7,11,15};
int target= 9;
int result[]=(find(arr,target));
System.out.println(result);
}
public static int[] find(int[] arr,int target){
Map<Integer,Integer> hm =new HashMap<>();
for(int i=0;i<arr.length;i++){
int num= target- arr[i];
if(hm.containsKey(num)){
return new int[]{hm.get(num),i};
}
hm.put(arr[i],i);
}
return new int[]{-1, -1};
}
}
So there are two ways you can do this. First of all, the output that you are getting is basically hash values. What you want to do is print out the elements in that array. The first way to do it is to iterate through your array and simply print out the values like so:
for(int j=0;j<result.length;j++){
System.out.println(result[j]);
}
The other way you could do this would be if you just used The Array class and its toString() method.
System.out.println(Arrays.toString(yourArray));
Both methods should work.
Your problem – which has been already answered – set aside, if you'd want to set up an environment in a single file, this might work OK for a Main.java file:
import java.util.*;
// import javafx.util.*;
class Solution {
public static final int[] twoSum(int[] nums, int target) {
int[] indices = new int[2];
HashMap<Integer, Integer> map = new HashMap<>();
for (int index = 0; index < nums.length; index++) {
if (map.get(target - nums[index]) != null) {
indices[1] = index;
indices[0] = map.get(target - nums[index]);
return indices;
}
map.put(nums[index], index);
}
return indices;
}
}
class Main {
public static void main(String[]args) {
Solution s = new Solution();
int arr[] = {2,7,11,15};
int target = 9;
System.out.println(s.twoSum(arr, target)[0]);
System.out.println(s.twoSum(arr, target)[1]);
}
}
Prints:
0
1
I am calling a method from another class. The method contains an integer array. I am trying to stay away from inputting the index manually.
I am trying to search for numbers within a range.
example:
ArrayList: {1,5}, {5,10}, {10,15}
Input: enter 3
Process: search for number within range
output: 1,5
The driver class is storing the objects from the main class called Numbers into ArrayList. The main class have an accessor call getNumbers. getNumbers contains an integer array with 2 elements. The driver is calling getNumbers to validate the entry that users input.
The code below works but I'm told it's consider bad coding to code entering the indexes. I want to know how to output the array from getNumber method without knowing the array length of getNumber?
example of what I have:
for(int i = 0; i < example.size(); i++)
//number is the integer that is inputted.
if(example.get(i).getNumbers()[1] > number &&
example.get(i).getNumbers()[0] <= numbers)
System.out.println(example.get(i));
Should I add another for loop?
example of what I am thinking of:
for(int i = 0; i < example.size(); i++)
for(int j = 0; j < example.get(i).getNumbers.length; j++){
if(example.get(i).getNumbers()[j] > number &&
example.get(i).getNumbers()[j] <= numbers)
System.out.println(example.get(i));
}
}
Edit: Changed how I worded some things and fixed the code of what I think I should do.
The code below works but I'm told it's consider bad coding to code
entering the indexes. I want to know how to output the array from
getNumber method without knowing the array length of getNumber ?
If you don't want to do the validations with array indexes for your first element and second element in the array, then you can solve the problem by modifying your Numbers class as shown below:
(1) Define two int variable members (currently you have only one)
(2) Add a method isInLimits(int input) to validate the range
(3) Override toString() which can be used to print the object as String
Numbers class (modified):
public static class Numbers {
private int firstElement;
private int secondElement;
public int getFirstElement() {
return firstElement;
}
public void setFirstElement(int firstElement) {
this.firstElement = firstElement;
}
public int getSecondElement() {
return secondElement;
}
public void setSecondElement(int secondElement) {
this.secondElement = secondElement;
}
//checks the input is in the range of this object elements
public boolean isInLimits(int input) {
if(input >= firstElement && input < secondElement) {
return true;
} else {
return false;
}
}
#Override
public String toString() {
return "{"+firstElement+","+secondElement+"}";
}
}
Usage of Numbers Class:
public static void main(String[] args) {
int userInput = 10; //get it from user
List<Numbers> example = new ArrayList<>();
//Add Numbers objects to example list
for(int i=0;i< example.size();i++) {
Number numberTemp = example.get(i);
//call Numbers object's isInLimits
if(numberTemp.isInLimits(userInput)) {
System.out.println(numberTemp);
}
}
}
In below code string is passed in a method with numbers separated by space,
now we need to provide sum of smallest two numbers in the string.
public class SumNearZero {
public static int SumNearZero(String s) {
String temp=s;
int t1=0;
for (int i = 0; i <s.length(); i++) {
if(temp.contains(" "))
{
t1++;
temp=temp.substring(temp.indexOf(" ")+1);
}
}
int a[]=new int[++t1];
int index=0;
for(int i=0; i<s.length(); i++)
{
if(s.contains(" "))
{
a[index]=Integer.parseInt(s.substring(0,s.indexOf(" ")));
s=s.substring(s.indexOf(" ")+1);
index++;
}
}
a[index]=Integer.parseInt(s);
for (int i = 0; i < a.length; i++) {
for(int j=0; j<a.length-1; j++)
{
int c=a[j],n=a[j+1];
if(c>n)
{
int t=c;
a[j]=n;
a[j+1]=t;
} } }
int result=a.length>1 ? a[0]+a[1]:a[0];
return result;
}
public static void main(String[] args) {
System.out.println(SumNearZero("35 96 10 20 5"));
}
}
Above code is working fine but i want to reduce the code. if you provide some suggestion regarding this, I'll be happy to learn from you.
Restrictions : use of Collections, predefined methods e.g(String.split(),Arrays.sort()...)
I would suggest you not perform your calculation and display in a constructor, create a static method and invoke it. Next, in that method, create a List of Integer by iterating the substrings generated by splitting your input on one (or more) white space characters. Then, sort the List. Finally, return the sum of the first two elements1. It's also a good to do some error checking for one number (or no numbers). That might look something like
public static int sumNearZero(String s) {
List<Integer> al = new ArrayList<>();
for (String str : s.split("\\s+")) {
al.add(Integer.parseInt(str));
}
if (al.isEmpty()) {
return 0;
}
Collections.sort(al);
if (al.size() == 1) {
return al.get(0);
}
return (al.get(0) + al.get(1));
}
Then invoke it like
public static void main(String[] args) {
System.out.println(sumNearZero("35 96 10 20 5"));
}
I get (as I expected)
15
1once sorted the first two are the minimum, and the last two are the maximum
You can make it faster by using for each loop instead of for loop every time, it is more recommended and faster approach whenever loop is increasing for array, lists etc.
Plus more you can get all numbers in string by using split function which retrives you array of those numbers.and then you can put your logic for getting small numbers.this will reduce counting and increase speed highly in general if you want to learn about optimization then this is definitive guide i suggest you to go through it. and see this answer.
Looks like an exercise, so not giving actual code.
Use String.split and Arrays.sort
I am building a data structure to learn more about java. I understand this program might be useless.
Here's what I want. I want to create a data structure that store smallest 3 values. if value is high, then ignore it. When storing values than I also want to put them in correct place so I don't have to sort them later. I can enter values by calling the add method.
so let's say I want to add 20, 10, 40, 30 than the result will be [10,20,30]. note I can only hold 3 smallest values and it store them as I place them.
I also understand that there are a lot of better ways for doing this but again this is just for learning purposes.
Question: I need help creating add method. I wrote some code but I am getting stuck with add method. Please help.
My Thinking: we might have to use a Iterator in add method?
public class MyJavaApp {
public static void main(String[] args){
MyClass<Integer> m = new MyClass<Integer>(3);
m.add(10);
m.add(20);
m.add(30);
m.add(40);
}
}
public class MyClass<V extends Comparable<V>> {
private V v[];
public MyClass(int s){
this.v = (V[])new Object[s];
}
public void add(V a){
}
}
Here is a rough sketch of the add method you have to implement.
You have to use the appropriate implementation of the compareTo method when comparing elements.
public void add(V a){
V temp = null;
if(a.compareTo( v[0]) == -1 ){
/*
keeping the v[0] in a temp variable since, v[0] could be the second
smallest value or the third smallest value.
Therefore call add method again to assign it to the correct
position.
*/
temp = v[0];
v[0] = a;
add(temp);
}else if(a.compareTo(v[0]) == 1 && a.compareTo(v[1]) == -1){
temp = v[1];
v[1] = a;
add(temp);
}else if(a.compareTo(v[1]) == 1 && a.compareTo(v[2]) == -1){
temp = v[2];
v[2] = a;
add(temp);
}
}
Therefore the v array will contain the lowerest elements.
Hope this helps.
A naive, inefficient approach would be (as you suggest) to iterate through the values and add / remove based on what you find:
public void add(Integer a)
{
// If fewer than 3 elements in the list, add and we're done.
if (m.size() < 3)
{
m.add(a);
return;
}
// If there's 3 elements, find the maximum.
int max = Integer.MIN_VALUE;
int index = -1;
for (int i=0; i<3; i++) {
int v = m.get(i);
if (v > max) {
max = v;
index = i;
}
}
// If a is less than the max, we need to add it and remove the existing max.
if (a < max) {
m.remove(index);
m.add(a);
}
}
Note: this has been written for Integer, not a generic type V. You'll need to generalise. It also doesn't keep the list sorted - another of your requirements.
Here's an implementation of that algorithm. It consists of looking for the right place to insert. Then it can be optimized for your requirements:
Don't bother looking past the size you want
Don't add more items than necessary
Here's the code. I added the toString() method for convenience. Only the add() method is interesting. Also this implementation is a bit more flexible as it respects the size you give to the constructor and doesn't assume 3.
I used a List rather than an array because it makes dealing with generics a lot easier. You'll find that using an array of generics makes using your class a bit more ugly (i.e. you have to deal with type erasure by providing a Class<V>).
import java.util.*;
public class MyClass<V extends Comparable<V>> {
private int s;
private List<V> v;
public MyClass(int s) {
this.s = s;
this.v = new ArrayList<V>(s);
}
public void add(V a) {
int i=0;
int l = v.size();
// Find the right index
while(i<l && v.get(i).compareTo(a) < 0) i++;
if(i<s) {
v.add(i, a);
// Truncate the list to make sure we don't store more values than needed
if(v.size() > s) v.remove(v.size()-1);
}
}
public String toString() {
StringBuilder result = new StringBuilder();
for(V item : v) {
result.append(item).append(',');
}
return result.toString();
}
}