I've created an array to generate 10 random numbers between 1-100, sorted them with a for loop (supposed to use the "enhanced for loop"). The last thing left besides making my for loop enhanced is to "enter one value, search array using binary search technique to determine if value is present or not and output that. Do you see what is wrong? Thanks!
import java.util.*;
class lab4point2 //lab4.2 part 1 {
public static void main(String args[]) {
int[] array = new int[10]; //array of 10 numbers created.
Random rand = new Random(); //random class created called rand.
for (int cnt = 0; cnt < array.length; cnt++) { //for loop to generate
array[cnt] = rand.nextInt(100) + 1; // the 10 numbers randomly 1-100
}
Arrays.sort(array); //sorted
System.out.println(Arrays.toString(array));// prints the 10 numbers to screen
System.out.print("Enter a value to see if it is present. ");
Scanner scanner = new Scanner(System.in);
int value = scanner.nextint();
boolean binarySearch(array, 0, 99, value);
int size = 100;
int low = 0;
int high = size - 1;
while (high >= low) {
int middle = (low + high) / 2;
if (data[middle] == value) {
System.out.print("Value is present ");
return true;
}
if (data[middle] < value) {
low = middle + 1;
}
if (data[middle] > value) {
high = middle - 1;
}
}
System.out.print("Value is not present. ");
return false;
}
}
You have some syntax errors in your code. It should look more like the following:
class SearchArray {
private final int[] array = new int[10];
private final Random random = new Random();
public SearchArray() {
for (int i = 0; i < array.length; i++) {
array[i] = random.nextInt(100) + 1;
}
Arrays.sort(array);
}
public String toString() {
return Arrays.toString(array);
}
public boolean contains(int value) {
int low = 0;
int high = array.length - 1;
while (high >= low) {
int middle = (low + high) / 2;
if (array[middle] == value) {
return true;
}
if (array[middle] < value) {
low = middle + 1;
}
if (array[middle] > value) {
high = middle - 1;
}
}
return false;
}
class lab4point2 {
public static void main(String args[]) {
SearchArray array = new SearchArray();
System.out.println(array.toString());
System.out.print("Enter a value to see if it is present. ");
Scanner scanner = new Scanner(System.in);
int value = scanner.nextint();
if (array.contains(value)) {
System.out.print("Value is present. ");
} else {
System.out.print("Value is not present. ");
}
}
}
Related
EDIT
try run in the main:
int[] arr = {646 ,94 ,366 ,754 ,948 ,678 ,121 ,320 ,528 ,36};
for(int i=0;i<10;i++){
System.out.println(randomizedSelect(arr,0,arr.length-1,5));
printArr(arr);
}
and see that i got diffrent outpot in each loop..
Got a little problem that I would like some help with, if anyone knows how.
I need to find the kth smallest value in an array by randomized partition.
I've got two problems:
I get array out of bounds with -1 and can't find a way to fix it.
Most of the time it works but sometimes it gives me wrong k place.
For example for array with length of 10, it tells me that 20 is in the 5th place but actually it should be in the 2nd place and it prints the array where not all the values on the left are smaller than 20 and not smaller than the 5th place.
Here is an example array:
{646 ,94 ,366 ,754 ,948 ,678 ,121 ,320 ,528 ,36}
The array input is done by a random number generator.
This is my code:
import java.util.Random;
import java.util.Scanner;
public class Main {
static Scanner scan = new Scanner(System.in);
static Random rand = new Random();
public static void main(String[] args) {
int nSize = askSizeN();
int kSize = askSizeK(nSize);
int[] arr = new int[nSize];
chose(arr);
int[] arrCopy = new int[nSize];
for (int i = 0; i < arrCopy.length; i++) {
arrCopy[i] = arr[i];
}
printArr(arrCopy);
System.out.println(randomizedSelect(arrCopy, 0, arr.length - 1, kSize));
printArr(arrCopy);
}
private static int partition(int[] arr, int p, int r) {
int x = arr[r];
int i = p - 1;
for (int j = p; j < r; j++) {
if (arr[j] <= x) {
i++;
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
int temp = arr[i + 1];
arr[i + 1] = arr[r];
arr[r] = temp;
return i + 1;
}
private static int randomizedPartition(int[] arr, int p, int r) {
int i = rand.nextInt(r - p);
int temp = arr[r];
arr[r] = arr[i];
arr[i] = temp;
return partition(arr, p, r);
}
private static int randomizedSelect(int[] arr, int p, int r, int i) {
if (p == r) {
return arr[p];
}
int q = randomizedPartition(arr, p, r);
int k = q - p + 1;
if (i == k) {
return arr[q];
}
else if (i < k) {
return randomizedSelect(arr, p, q - 1, i);
}
else {
return randomizedSelect(arr, q + 1, r, i - k);
}
}
private static int askSizeN() {
System.out.println("Please chose the size of the heap: \n" + "(the size of n)");
return scan.nextInt();
}
private static int askSizeK(int nSize) {
System.out.println(
"Please chose how much small values you want to see: \n" + "(the size of k)");
int kSize = scan.nextInt();
if (kSize > nSize) {
System.out.println("cant print more number then the size of the Heap..");
System.out.println("Please enter a number less then " + (nSize + 1));
askSizeK(nSize);
}
return kSize;
}
private static int[] chose(int[] a) {
System.out.println("Chose the option you want: \n" + "\t1. enter your own values."
+ "\n\t2. let me generate random values");
int chose = scan.nextInt();
if (chose == 1) {
for (int i = 0; i < a.length; i++) {
System.out.println("Enter value number " + (i + 1));
a[i] = scan.nextInt();
}
}
else if (chose == 2) {
System.out.println("Generate random numbers.");
for (int i = 0; i < a.length; i++) {
a[i] = rand.nextInt(1000);
}
}
else {
chose(a);
}
return a;
}
private static void printArr(int[] a){
for(int i=0;i<a.length;i++){
System.out.print(a[i] + " ");
}
System.out.println();
}
}
I've solved the problem.
Method randmizedPartition() was generating wrong random pivot for partition.
I solved it by changing the random line to:
int i = rand.nextInt((r - p) + 1) + p;
I am trying to find the minimum pair of numbers to achieve sum of 15. I am creating new array for them and passing that array to method which is adding element of that array and generating true or false. array size will increase if method returns false.
public class FindMinimum {
static int arr[] = { 10, 3, 2, 13 };
static int numArr[] = new int[30];
static int arrLength = 2;
static boolean status = false;
static int number;
public static void main(String args[]) {
for (int i = 0; i < arrLength; i++) {
numArr[i] = arr[i];
}
if (checkPair(numArr)) {
System.out.println("Number found");
} else {
arrLength = arrLength + 1;
System.out.println("Increasing array length by one");
}
}
public static boolean checkPair(int x[]) {
for (int i = 0; i < x.length; i++) {
number = number + x[i];
}
if (number == 15) {
status = true;
for (int i : x) {
System.out.println(i);
}
} else {
status = false;
}
return status;
}
}
Expected result is minimum pair of addition that is "13 ,2"
If I understand correctly need to find minimum pair which always add to 15. If this is correct below code should solve it.
public static void main(String args[]) {
Arrays.sort(arr);
for (int i=0,j=arr.length-1;i<arr.length && j>=0;) {
if ((arr[i]+arr[j])<15) {
/*System.out.println(arr[i]+"-"+arr[last-i]);
break;*/
i++;
} else if ((arr[i]+arr[j])>15) {
j--;
} else {
System.out.println(arr[i]+"-"+arr[j]);
break;
}
}
}
import java.util.Scanner;
public class FindMinimumPair {
static Scanner sc = new Scanner(System.in);
static int userArr[];
static int numArr[]; // New array to take number / pairs from main array to compare with else numbers
// in the main array
static int arrLength = 1; // increase the array length of numArr if pair is more than 2 numbers
static boolean status = false; // check method returns true or false
static int sum;
public static void main(String args[]) {
System.out.println("Sum of pair should be ?");
sum = sc.nextInt();
System.out.println("Enter the lenght of an array");
int userArrLength = sc.nextInt();
userArr = new int[userArrLength];
System.out.println("Enter array integers upto " + userArrLength);
for (int i = 0; i < userArrLength; i++) {
userArr[i] = sc.nextInt();
}
// Loop to read numbers from main array
for (int i = 0; i < userArr.length; i++) {
// Defines the length of new array
numArr = new int[arrLength]; // initialize the new array
// Loop to add numbers into new array
for (int j = 0; j < arrLength; j++) {
numArr[j] = userArr[j]; // add numbers into new array
}
if (check(numArr)) { // call check method and pass new array in it
for (int a : numArr) { // if returns true then print that array (contains the pair)
System.out.print(a + " ");
}
System.out.print(userArr[numArr.length]); // print the last number which is the part of numArr
System.out.println(" is equals to " + sum);
} else {
System.out.println("Numbers not found");
}
arrLength = arrLength + 1; // increase the array length if false
}
}
public static boolean check(int number[]) {
int x = 0;
// Loop to make sum of all numbers of numArr (make it single number)
for (int j = 0; j < number.length; j++) {
x = x + number[j];
}
outer: for (int i = 0; i < number.length; i++) { // loop for elements in numArr array
for (int j = 0; j < userArr.length; j++) { // loop for given array elements
if (x + userArr[j] == sum) { // check each number of given array with the sum of numArr
status = true;
break outer; // breaks outer loop and returns true
} else {
status = false;
}
}
}
return status;
}
}
I was wondering how to work with negative values and a negative target, right now my program gives index out of bounds errors whenever negative values are given to these variables. I need my hasSum function work with negative values for this project, I can't just assume positive.
import java.util.Stack;
import java.util.Scanner;
public class subsetSum {
static Scanner input = new Scanner(System.in);
static {
System.out.print("Enter the target (T)" + "\n");
}
/** Set a value for target sum */
static int TARGET_SUM = input.nextInt(); //this is the target
/** Store the sum of current elements stored in stack */
static int sumInStack = 0;
Stack<Integer> stack = new Stack<Integer>();
public static void main(String[] args) {
//the size is S
System.out.println("\n" + "Enter the size of the set (S)");
int values = input.nextInt(); //size = "values"
//value of each size entry
System.out.println("\n" + "Enter the value of each entry for S");
int [] numbers = new int[values];
for(int i = 0; i < values; i++) //for reading array
{
numbers[i] = input.nextInt();
}
if(hasSum(numbers, TARGET_SUM)){
System.out.println("\n" + "Can: ");
subsetSum get = new subsetSum(); // encapsulation
get.populateSubset(numbers, 0, numbers.length);
}else{
System.out.println("\n" + "Cannot");
}
}
//method based on dynamic programming O(sum*length)
public static boolean hasSum(int [] array, int sum)
{
int i;
int len = array.length;
boolean[][] table = new boolean[sum + 1][len + 1]; //this has to be changed for negative
//If sum is zero; empty subset always has a sum 0; hence true
for(i = 0; i <= len; i++){
table[0][i] = true;
}
//If set is empty; no way to find the subset with non zero sum; hence false
for(i = 1; i <= sum; i++){
table[i][0] = false;
}
//calculate the table entries in terms of previous values
for(i = 1; i <= sum; i++)
{
for(int j = 1; j <= len; j++)
{
table[i][j] = table[i][j - 1];
if(!table[i][j] && i >= array[j - 1]){
table[i][j] = table[i - array[j - 1]][j - 1];
}
}
}
return table[sum][len]; //this has to be changed for negative
}
public void populateSubset(int[] data, int fromIndex, int endIndex) {
/*
* Check if sum of elements stored in Stack is equal to the expected
* target sum.
*
* If so, call print method to print the candidate satisfied result.
*/
if (sumInStack >= TARGET_SUM) {
if (sumInStack == TARGET_SUM) {
print(stack);
}
// there is no need to continue when we have an answer
// because nothing we add from here on in will make it
// add to anything less than what we have...
return;
}
for (int currentIndex = fromIndex; currentIndex < endIndex; currentIndex++) {
if (sumInStack + data[currentIndex] <= TARGET_SUM) {
stack.push(data[currentIndex]);
sumInStack += data[currentIndex];
/*
* Make the currentIndex +1, and then use recursion to proceed
* further.
*/
populateSubset(data, currentIndex + 1, endIndex);
sumInStack -= (Integer) stack.pop();
}
}
}
/**
* Print satisfied result. i.e. 5 = 1, 4
*/
private void print(Stack<Integer> stack) {
StringBuilder sb = new StringBuilder();
for (Integer i : stack) {
sb.append(i).append(",");
}
// .deleteCharAt(sb.length() - 1)
System.out.println(sb.deleteCharAt(sb.length() - 1).toString());
}
}
Are you trying to find a sum of subset or a subarray?
If a subset, then a simple recursion could do the trick, e.g.:
public static boolean hasSum(int [] array, int sum)
{
return hasSum(array, 0, 0, sum);
}
private static boolean hasSum(int[] array, int index, int currentSum, int targetSum) {
if (currentSum == targetSum)
return true;
if (index == array.length)
return false;
return hasSum(array, index + 1, currentSum + array[index], targetSum) || // this recursion branch includes current element
hasSum(array, index + 1, currentSum, targetSum); // this doesn't
}
If you're trying to find a subarray, I'd use prefix sums, e.g.:
public static boolean hasSum(int [] array, int sum)
{
int[] prefixSums = new int[array.length];
for (int i = 0; i < prefixSums.length; i++) {
prefixSums[i] = (i == 0) ? array[i] : array[i] + prefixSums[i - 1];
}
for (int to = 0; to < prefixSums.length; to++) {
if (prefixSums[to] == sum)
return true; // interval [0 .. to]
for (int from = 0; from < to; from++) {
if (prefixSums[to] - prefixSums[from] == sum)
return true; // interval (from .. to]
}
}
return false;
}
BTW I think reading the input values from Scanner inside the static initializer is a bad idea, why don't you move them to main()?
I was practicing with some exercises from UVA Online Judge, I tried to do the Odd sum which basically is given a range[a,b], calcule the sum of all odd numbers from a to b.
I wrote the code but for some reason I don't understand I'm getting 891896832 as result when the range is [1,2] and based on the algorithm it should be 1, isn't it?
import java.util.Scanner;
public class OddSum
{
static Scanner teclado = new Scanner(System.in);
public static void main(String[] args)
{
int T = teclado.nextInt();
int[] array = new int[T];
for(int i = 0; i < array.length; i++)
{
System.out.println("Case "+(i+1)+": "+sum());
}
}
public static int sum()
{
int a=teclado.nextInt();
int b = teclado.nextInt();
int array[] = new int[1000000];
for (int i = 0; i < array.length; i++)
{
if(a%2!=0)
{
array[i]=a;
if(array[i]==(b))
{
break;
}
}
a++;
}
int res=0;
for (int i = 0; i < array.length; i++)
{
if(array[i]==1 && array[2]==0)
{
return 1;
}
else
{
res = res + array[i];
}
}
return res;
}
}
Your stopping condition is only ever checked when your interval's high end is odd.
Move
if (array[i] == (b)) {
break;
}
out of the if(a % 2 != 0) clause.
In general, I don't think you need an array, just sum the odd values in your loop instead of adding them to the array.
Keep it as simple as possible by simply keeping track of the sum along the way, as opposed to storing anything in an array. Use a for-loop and add the index to the sum if the index is an odd number:
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter minimum range value: ");
int min = keyboard.nextInt();
System.out.println("Enter maximum range value: ");
int max = keyboard.nextInt();
int sum = 0;
for(int i = min; i < max; i++) {
if(i % 2 != 0) {
sum += i;
}
}
System.out.println("The sum of the odd numbers from " + min + " to " + max + " are " + sum);
}
I don't have Java installed right now, however a simple C# equivalent is as follows: (assign any values in a and b)
int a = 0;
int b = 10;
int result = 0;
for (int counter = a; counter <= b; counter++)
{
if ((counter % 2) != 0) // is odd
{
result += counter;
}
}
System.out.println("Sum: " + result);
No major dramas, simple n clean.
For my current homework, I'm trying to sort my array through a generic class as the user inserts values into its locations. When the size reads as fully loaded, the array class calls in an expansion method that increases the size of the array while retaining its values in proper locations, which I followed from my Professor's note. For some reason, all my values except for location[0] seem to either be misplaced or erased from the array. I'm leaning that the problem originates in the expansion method but I have no idea how to fix this.
For example, the initial size is currently set to 5 but increments by 3 when expansion method is called. The user can input values 1,2,3,4,5 perfectly. But expansion is called when user inputs new value 6 that outputs an array of 1, 6, null, null, null, null. Any further will lead to the error "Exception in thread "main" java.lang.NullPointerException"
Here is my Sorted Array class:
public class SortedArray {
private int size;
private int increment;
private int top;
Comparable[] a;
public SortedArray(int initialSize, int incrementAmount)
{
top = -1;
size = initialSize;
increment = incrementAmount;
a = new Comparable [size];
}
public int appropriatePosition(Comparable value)
{
int hold = top;
if(hold == -1)
{
hold = 0;
}
else
{
for(int i = 0; i <= top; i++)
{
if(value.compareTo(a[i]) > 0)
{
hold = i + 1;
}
}
}
return hold;
}
public Comparable smallest()
{
return a[0];
}
public Comparable largest()
{
return a[top];
}
public void insert(Comparable value)// the method that my driver calls for.
{
int ap = appropriatePosition(value);
//Expansion if full
if(full() == true)
{
expansion();
}
//Shifting numbers to top
for(int i = top; i >= ap ; i--)
{
{
a[i + 1] = a[i];
}
}
a[ap] = value;
top++;
}
public boolean full()
{
if(top == a.length -1)
{
return true;
}
else
{
return false;
}
}
public void expansion()//here's where the expansion begins
{
int newSize = a.length + increment;
Comparable[] tempArray = new Comparable[newSize];
for(int i= 0; i < a.length; i++)
{
tempArray[i]= a[i];
a = tempArray;
}
}
Here's my driver class that calls for the insert method in SortedArray class.
public class IntDriver {
public static void main(String[] args)
{
Scanner keyboard = new Scanner(System.in);
//Creating variables
int data;
boolean check = false;
int choice;
int size = 5;
int increment = 3;
SortedArray b = new SortedArray(size, increment);
//Creating Menu
System.out.println("Please choose through options 1-6.");
System.out.println("1. Insert\n2. Delete\n3. Clear\n4. Smallest\n5. Largest\n6. Exit\n7.Redisplay Menu");
while(check == false)
{
choice = keyboard.nextInt();
switch(choice)
{
case 1:
System.out.println("Type the int data to store in array location.");
data = keyboard.nextInt();
Integer insertObj = new Integer(data);
b.insert(insertObj);
System.out.println("The value " + data + " is inserted");
b.print();
break;
In the expansion method, you're replacing a too soon. The replacement should happen after the for loop:
public void expansion()//here's where the expansion begins
{
int newSize = a.length + increment;
Comparable[] tempArray = new Comparable[newSize];
for(int i= 0; i < a.length; i++)
{
tempArray[i]= a[i];
}
a = tempArray;
}