I'm very new to binary search and I attempted a code that would read values from a document and then the user can input a number to search for from the document, and through binary search, the number would be found. I'm having trouble now because the "low" variable that I initialize in the binary search section of my code is not being returned to my main code and there's an error that says "low can not be resolved to a variable".
Here is the code for my binary search:
static public int search (int[]numbers,int target, int count)
{
int high = numbers.length;
int low = -1;
int middle = (high+low)/2;
while(high-low>1)
{
count++;
middle = (high+low)/2;
if(numbers[middle]>target)
{
high = middle;
}
else if(numbers[middle]<target)
{
low = middle;
}
else
{
break;
}
System.out.println(numbers[middle]);
System.out.println(middle);
}
if(low == -1 || numbers[low]!=target)
{
low=-1;
return low;
}
else
{
return low;
}
}
And here is the code from my main code. The part with the if statements is where the error is showing up:
public static void main(String[] args) throws IOException {
DataInputStream input = new DataInputStream(System.in);
int [] numbers = new int [50000];
int target;
int count=0;
try
{
BufferedReader br = new BufferedReader(new FileReader("randNums.txt"));
for(int i=0;i<50000;i++)
{
numbers[i]=Integer.parseInt(br.readLine());
}
br.close();
Arrays.sort(numbers);
System.out.print("Choose a number between 1-100000000 to search for: ");
target = Integer.parseInt(input.readLine());
search(numbers, target,count);
if(low==-1)
{
System.out.println("The number was not on the list.");
}
else
{
System.out.println("The number is at position " + low);
System.out.println("It took " + count + " comparisons to find the number.");
}
}
You have to initialize low in main:
int low=search(numbers, target,count);
I have Already resolved this algorithm.
Try my code :
public static int guessNumber(int number) {
int first = 0;
int last = 1_000_000;
if (verify(first) == 0) {
count++;
return first;
}
if (verify(last) == 0) {
count++;
return last;
}
while (last > first && count <= 50) {
count += 1;
// get the middle of the range
int middle = (first + last) / 2;
if (verify(middle) == 0) {
return middle;
}
if (verify(middle) == 1) {
first = middle + 1;
if (verify(first) == 0) {
return first;
}
}else {
last = middle - 1;
if (verify(last) == 0)
return last;
}
}
return 0;
}
//Function verify(integer) => integer
public static int verify(int guess){
if (numberTobeGuessed > guess ) {
return 1;
}else if (numberTobeGuessed < guess) {
return -1;
}
return 0;
}
I recently found a solution for lazy peoples like me use below code
int position = Arrays.binarySearch(numbers , target);
here no need to sort, and array variable number integer variable target.
i am getting a little problem and i really do not know why. i am trying to program to search for a number input by the user using a binary searching method. it works well when the number in the middle of the array is searched for but when i attempt to search any other number am getting an error. here is my code.
import java.util.Scanner;
public class Main {
public static void main(String args[])
{
//declaring array
int array[] = {12,23,34,45,56,67,78,89};
//declaring variables
int search = 0;
Scanner input = new Scanner(System.in);
System.out.print("\n Enter: ");
search = input.nextInt();
binarySearch(array, search);
}//end of main
static public void binarySearch(int[] array, int search)
{
int begin = 0;
int end = array.length-1;
int mid = 0;
boolean found = false;
while(!found)
{
mid = (begin + end)/2;
if(array[mid] == search)
{
found = true;
search = array[mid];
}
else if(array[mid] < search)
{
begin = array[mid+1];
}
else if(array[mid] > search)
{
end = array[mid-1];
}
}//end of while loop
//if(!found)
//return ("BOOHOO your search was not found");
System.out.print("Yippee i found "+ search + " at index " + mid);
}
}//end of class
When you don't find a search, you need to reset your begin and end pointers to the indexes and not on the values on those indexes i.e.
while(!found)
{
mid = (begin + end)/2;
if(array[mid] == search)
{
found = true;
}
else if(array[mid] < search)
{
begin = mid+1;
}
else if(array[mid] > search)
{
end = mid-1;
}
}//end of while loop
Hy there. Below you can see sagment of my code. So lets go to the problem.
int i is not returning correct values and i cannot figure it out why.
LIST: [AGRFT, AGRFT, ARNES, ASCII, ASEAN, Aaron, Abdul, Abdul]
So for example. User inputs AS***, the program should return i is at 2. However i am getting i is at 0.
If i remember right it should go like this:
User_input= AS***
User_input.lenght() should be 5
first it should be user_input.charAt(0)=='*' NO
second it should be user_input.charAt(1)=='*' NO
third it should be user_input.charAt(2)=='*' YES
BREAK
i is at 2.
SO what am i missing?
I am getting 0.
Oh and also at
for(i=0; i < user_input.length();i++){
i am getting warning that i++ is Dead code?
if (dolzina == 5) {
for(i=0; i < user_input.length();i++){
if (user_input.charAt(i)=='*');
break;
}
System.out.println("i is at "+ i);
this is my full code for refrence. What it does it reads from txt file add wor
public class proba {
public static void main(String[] args) {
String izbira;
int dolzina=0;
int i=0;
Scanner in = new Scanner(System.in);
String user_input;
Scanner input = new Scanner(System.in);
String regex;
List<String> list5 = new ArrayList<String>();
int beseda;
String prefix = null;
try {
File file = new File("sort.txt");
FileReader fileReader = new FileReader(file);
BufferedReader bufferedReader = new BufferedReader(fileReader);
String vrstica;
while ((vrstica = bufferedReader.readLine()) != null) {
if (vrstica.length() == 5) {
list5.add(vrstica);
}
}
System.out.println(list5);
do{
do {
System.out.println("Enter lenght of word:");
if (in.hasNextInt()) {
dolzina = in.nextInt();
} else if (in.hasNextLine()) {
System.out.printf("Wrong entry!%n ",
in.nextLine());
}
} while (dolzina <= 0);
Collections.sort(list5);
System.out.println("Enter a word for unknown character enter * :");
user_input = input.nextLine();
System.out.println("Sorted list: [length: " + list5.size() + "]");
if (dolzina == 5) {
for(i=0; i < user_input.length();i++){
if (user_input.charAt(i)=='*');
break;
}
System.out.println("i je"+ i);
prefix=user_input.substring(0,i);
System.out.println(prefix);
int start=binarySearchfirst(list5,prefix);
int end=binarySearchlast(list5,prefix);
System.out.println(start);
System.out.println(end);
for (int b=start;b<=end;b++)
{
user_input = user_input.replace("*", ".");
String s = (String) list5.get(b);
if (s.matches(user_input))
System.out.println(s);
}
}
dolzina=-1;
System.out.println("Ponovni vnos (da/ne):");
Scanner inn= new Scanner (System.in);
izbira = inn.next();
}while (izbira.equalsIgnoreCase("da"));
bufferedReader.close();
} catch (IOException e) {
e.printStackTrace();
}}
public static int binarySearchfirst(List<String> integerList, String prefix) {
int low = 0;
int high = integerList.size() - 1;
while (low <= high) {
int mid = (low + high) / 2;
if (integerList.get(mid).startsWith(prefix)) {
if (mid == 0 || !integerList.get(mid - 1).startsWith(prefix)) {
return mid;
} else {
high = mid - 1;
}
} else if (prefix.compareTo(integerList.get(mid)) > 0) {
low = mid + 1;
} else {
high = mid - 1;
}
}
return low;
}
public static int binarySearchlast(List<String> integerList, String prefix) {
int low = 0;
int high = integerList.size()-1;
while (low <= high) {
int mid = (low+high)/2;
if (integerList.get(mid).startsWith(prefix)) {
if (mid == integerList.size()-1 || !integerList.get(mid+1).startsWith(prefix)) {
return mid;
}
else {
low = mid+1;
}
}
else if (prefix.compareTo(integerList.get(mid)) > 0) {
low = mid+1;
}
else {
high = mid-1;
}
}
return high;
}
}
You have an extra semi-colon after your if statement:
for(i=0; i < user_input.length();i++)
{ if (user_input.charAt(i)=='*');
break;
}
So the break is executed the first time through the loop no matter what. This is also why i++ is being reported as dead code...it's never being executed.
I have the below snippet of code to use a recursive method to add the sum of odd numbers.
I have already coded the iterative method successfully that adds the sum of all odd numbers between n and m which are entered by the user. I'd like to reach that goal but am started slow to make sure I understand what is happening.
I know that it makes more sense to do it iteratively, however I am experimenting with the two types to see which is more efficient. I am stuck on the below as it is not doing what i want it to and i can't understand why.
import java.util.*;
public class SumofOdd
{
public static void main (String [] args)
{
int n = 0;
Scanner sc = new Scanner(System.in);
System.out.println("Please enter an odd number");
n = sc.nextInt();
int x = add(n);
}
public static int add(int x)
{
if (x == 0)
{
return 0;
}
else
{
return (x + add(x-1));
}
}
}
I have changed the above to the below. It compiles however stops after I enter the number.
import java.util.*;
public class SumofOdd
{
public static void main (String [] args)
{
int n = 0;
Scanner sc = new Scanner(System.in);
System.out.println("Please enter an odd number");
n = sc.nextInt();
if (n%2 == 0)
{
System.out.println("The number entered is even");
}
else
{
int x = add(n);
}
}
public static int add(int x)
{
if (x <= 0)
{
return 0;
}
else
{
return (x + add(x-2));
}
}
}
import java.util.*;
public class OddR{
public static void main (String Args [])
{
Scanner s = new Scanner(System.in);
System.out.println("Enter an odd number");
int max = s.nextInt();
if((max% 2) == 0) {
System.out.println(max + " is Even number and therefore is invalid");
}
else{
System.out.println("Enter a greater odd number");
int m = s.nextInt();
if (m <max){
System.out.println("Invalid data");
}
else{
if((m % 2) == 0) {
System.out.println(m + " is Even number and therefore is invalid");
}
else{
int data = (addodd(m)- addodd(max))+max;
System.out.print("sum:"+data);
}
}
}
}
public static int addodd(int m)
{
if(m<=0)
{
return 0;
}
if(m%2 != 0)
{
return (m+addodd(m-1));
}
else
{
return addodd(m-1);
}
}
}
This is the answer recursively of the sum of odd numbers from n to m
public int addOdds(int n) {
if (n <= 0) {
return 0;
}
if (n % 2 == 0) {
return addOdds(n - 1);
}
return x + addOdds(n - 1);
}
Take care, I never tested the code.
class Oddsum {
public int addodd(int n)
{
if(n<=0)
{
return 0;
}
if(n%2 != 0)
{
return (n+addodd(n-1));
}
else
{
return addodd(n-1);
}
}
}
public class Xyz {
public static void main (String[] v)
{
int n = 9;
Oddsum o = new Oddsum();
int data = o.addodd(n);
System.out.print("sum:"+data);
}
}
This is working fine
public static void main (String[] args){
public static int oddSum(int s){
if (s <= 0)
return 0;
else
return s + oddSum(s -2);
}
}
I want to convert a string input like 2,3,6,7,8,10,12,14,15,16 to 2-3,6-8,10,12,14-16 using java
I tried using the below code
Vector ar=new Vector();
int lastadded=0;
String ht="";
String [] strarray=str.split(",");
strarray=sortArray(strarray);
Vector intarray=new Vector();
for(int i=0;i<strarray.length;i++)
{
int temp=1;
for(int j=1;j<=intarray.size();j++)
{
if(Integer.parseInt(strarray[i])==Integer.parseInt(intarray.get(j-1).toString()))
{
temp=0;
}
}
if(temp==1)
{
intarray.add(Integer.parseInt(strarray[i]));
ar.add(Integer.parseInt(strarray[i]));
}
}
ht="";
String strdemo="";
for(int i=0;i<intarray.size();i++)
{
if(ht=="")
{
ht=ar.get(i)+"";
lastadded=i;
}
else
{
strdemo=(String)ht;
if(strdemo.length()==ar.get(0).toString().length())
{
if(Integer.parseInt(strdemo.substring(0))==Integer.parseInt(ar.get(i).toString())-1)
{
strdemo=strdemo+"-"+ar.get(i);
lastadded=Integer.parseInt(ar.get(i).toString());
ht=strdemo;
}
else
{
strdemo=strdemo+","+ar.get(i);
lastadded=Integer.parseInt(ar.get(i).toString());
ht=strdemo;
}
}
else if(strdemo.length()==3)
{
strdemo=(String)ht;
if(Integer.parseInt(strdemo.substring(strdemo.length()-1,strdemo.length()))==Integer.parseInt(ar.get(i).toString())-1)
{
strdemo=strdemo.substring(0,strdemo.length()-2)+"-"+Integer.parseInt(ar.get(i).toString());
lastadded=Integer.parseInt(ar.get(i).toString());
ht=strdemo;
}
else
{
strdemo=strdemo+","+Integer.parseInt(ar.get(i).toString());
lastadded=Integer.parseInt(ar.get(i).toString());
ht=strdemo;
}
}//Else IF
else{
strdemo=(String)ht;
int de=1;
int ddd=lastadded;
if(ddd==Integer.parseInt(ar.get(i).toString())-1)
{
int lastaddedlen=(lastadded+"").length();
String symbol=strdemo.substring(strdemo.length()-lastaddedlen-1,strdemo.length()-lastaddedlen);
if(symbol.equalsIgnoreCase("-"))
strdemo=strdemo.substring(0,strdemo.length()-lastaddedlen-1)+"-"+Integer.parseInt(ar.get(i).toString());
else
strdemo=strdemo+"-"+Integer.parseInt(ar.get(i).toString());
lastadded=Integer.parseInt(ar.get(i).toString());
ht=strdemo;
}
else
{
strdemo=strdemo+","+Integer.parseInt(ar.get(i).toString());
lastadded=Integer.parseInt(ar.get(i).toString());
ht=strdemo;
}
}
}
}
Here sortArray function sorts the array descending and returns
protected static String[] sortArray(String ss[])
{
String temp;
for(int i=0;i<ss.length;i++)
{
for(int j=0;j<ss.length;j++)
{
if(Integer.parseInt(ss[i])<Integer.parseInt(ss[j]))
{
temp=ss[i];
ss[i]=ss[j];
ss[j]=temp;
}
}
}
return ss;
}
I am not getting consistant results for some inputs for example for the below case
2,3,6,7,8,10,12,14,15,16 it gives 2-3,6-8,10,12,14-16 (which is correct)
while for 2,4,5,6,7,8,10,12,14,15,16 it gives 2-8,10,12,14-16 (which actually should have been 2,4-8,10,12,14-16)
Where does the code go inconsistent is what I need to find out..
This is pretty ugly and verbose in Java, but here is a version. Note, it uses StringUtils from Spring at the very end for the trivial but also ugly process of converting a String collection to a comma delimited string.
The key is to use a separate class to model the numeric ranges. Let this class know how to turn itself into a String. Then you won't have so much logic around appending to a StringBuilder.
Also, try to think in terms of collections. This always makes things clearer. The pseudo-code is something like: String becomes List<Integer> becomes List<Range> and finally becomes String.
public class Ranges {
// A class that models a range of integers
public static class Range {
private int low;
private int high;
public Range(int low, int high) {
this.low = low;
this.high = high;
}
public int getHigh() {
return high;
}
public void setHigh(int high) {
this.high = high;
}
#Override
public String toString() {
return (low == high) ? String.valueOf(low) : String.format("%d-%d", low, high);
}
}
public static void main(String[] args) {
String input = "2,3,6,7,8,10,12,14,15,16";
// Turn input string into a sorted list of integers
List<Integer> inputNumbers = new ArrayList<Integer>();
for (String num : input.split(",")) {
inputNumbers.add(Integer.parseInt(num));
}
Collections.sort(inputNumbers);
// Flatten list of integers into a (shorter) list of Ranges
Range thisRange = null; // the current range being built
List<Range> ranges = new ArrayList<Range>();
for (Integer number : inputNumbers) {
if (thisRange != null && number <= thisRange.getHigh() + 1) {
// if we are already building a range (not null) && this new number is
// the old high end of the range + 1, change the high number.
thisRange.setHigh(number);
} else {
// create a new range and add it to the list being built
thisRange = new Range(number, number);
ranges.add(thisRange);
}
}
// Join List<String> into a single String
String result = StringUtils.collectionToCommaDelimitedString(ranges);
System.out.println("result = " + result);
}
}
Here is my implementation. Hope this help.
You have to pass these values
e.g int[] a = {2,3,4,5,6,7,8,10,12, 14,15,16,18,19,21,22,26};
to the following method.
public List<String> listIntRange(int[] values)
{
List<String> intRangeList = new ArrayList<String>();
int first = 0;
int current = 0;
int prev = 0;
int count = 0;
if (values == null || values.length < 1)
return intRangeList;
first = prev = values[0];
int index = 1;
boolean range = false;
for(index = 1; index < values.length; index++)
{
current = values[index];
if(current - prev == 1)
{
range = true;
prev = current;
continue;
}
if(range == true)
{
intRangeList.add(first + "-" + prev);
}
else
{
intRangeList.add("" + first);
}
first = current;
prev = current;
range = false;
}
if(range == true)
{
intRangeList.add(first + "-" + current);
}
else
{
intRangeList.add("" + current);
}
return intRangeList;
}
Output is as follows, when print out the values from intRangeList:
2-8,10,12,14-16,18-19,21-22,26,
Please ignore last comma ','.