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Tough Algorithm - Do not let the same character repeat for n positions

I wasn't able to figure this one out since I don't know how to calculate "inserting" an underscore. I included my attempt at solving this problem.
Given a string, do not let the same character repeat for n positions. If it does repeat, insert an underscore to push
it X positions down. The final output needed is just the total number of characters.
Example 1) Input "QQ",2 becomes "Q__Q", the return value is 4.
Example 2) Input "ABCA",2 becomes "ABCA" (no spaces needed), total characters is 4.
Example 3) Input "DEDEE", 1 becomes "DEDE_E", total chars is 6.
Example 4) Input "JKJK", 2 becomes "JK_JK", total characters is 5 (The toughest example).
import java.lang.Math;
import java.util.HashMap;
import java.util.ArrayList;
public class Spacer {
public static void main (String args[]) {
System.out.println("QQ,2 = " + spacey("QQ", 2) + ", expected 4");
System.out.println("ABCA,2 = " + spacey("ABCA",2) + ", expected 4");
System.out.println("DEDEE,1 = " + spacey("DEDEE", 1) + ", expected 6");
System.out.println("JKJK,2 = " + spacey("JKJK", 2) + ", expected 5");
}
private static int spacey(String word, int spaces) {
// int shift = 0;
HashMap<Character, Integer> hm = new HashMap<>();
for (int i=0; i<word.length(); i++) {
char letter = word.charAt(i);
System.out.println(i + "=" + letter + " last saw " + hm.get(word.charAt(i)));
if (hm.get(letter) == null) {
hm.put(letter, i);
} else {
System.out.println(i + "-" + hm.get(letter) + "<=" + spaces);
if (i - hm.get(word.charAt(i)) <= spaces) {
// System.out.println("add " + (spaces + 1 - (i - hm.get(letter))));
// shift += (spaces + 1) - (i - hm.get(letter));
word = word.substring(0, i) + "_" + word.substring(i);
System.out.println(i + " word=" + word);
}
hm.put(letter, i); // update the hashmap with the last seen again
}
}
return word.length();
}
}

Your question is (mainly) about inserting underscores. A key insight that can help move forward is that the input and output strings are different, so it would be cleaner to treat them as such, using a StringBuilder for example. Additionally, it doesn't hurt at this stage to use temporary variables to capture concepts such as distance between characters. Leveraging these two ideas, you can have more self-explanatory code, for example:
public static String space(String input, int spaces) {
HashMap<Character, Integer> map = new HashMap<>();
StringBuilder result = new StringBuilder();
for( char symbol : input.toCharArray() ) {
int position = result.length();
int lastPosition = map.getOrDefault(symbol, position-spaces-1);
int distance = position - lastPosition -1;
for( int j = 0; j < Math.max( spaces - distance, 0) ; j++ ) {
result.append('_');
}
result.append(symbol);
map.put(symbol, result.length()-1);
}
return result.toString();
}
(and once this is mastered and digested, it's of course possible to in-line the temps)

The requirement doesn't ask you to display the constructed string so we need to only do calculations. The regex (.+)\1 will match any repetition of 1 or more chars and countPattern returns how many times that pattern was found.
public static void main(String[] args) {
System.out.println("QQ,2 = " + spacey("QQ", 2) + ", expected 4");
System.out.println("ABCA,2 = " + spacey("ABCA",2) + ", expected 4");
System.out.println("DEDEE,1 = " + spacey("DEDEE", 1) + ", expected 6");
System.out.println("JKJK,2 = " + spacey("JKJK", 2) + ", expected 6"); //in becomes JK__JK, ie. 4 + 2x'_'
}
private static int spacey(String word, int spaces) {
if(spaces<0){
throw new IllegalArgumentException("should be positive value");
}
if(word==null){
return 0;
}
if(spaces==0){
return word.length();
}
final Pattern repeatedCharRegex = Pattern.compile("(.+)\\1");
final int repetitions = countPattern(word, repeatedCharRegex);
return word.length() + repetitions*spaces;
}
public static int countPattern(String references, Pattern referencePattern) {
Matcher matcher = referencePattern.matcher(references);
int count = 0;
while (matcher.find()){
count++;
}
return count;
}

First of all you have an error in one of your test cases. Assuming you want to reproduce the cases in the quoted challenge, you need a 1 as second argument to the call to spacey here:
System.out.println("DEDEE,1 = " + spacey("DEDEE", 1) + ", expected 6");
// ^ ^
The formula to calculate the number of underscores to insert is:
previousindex + n + 1 - i
...where previousindex is the index at which the current letter occurred before, and i is the current index.
You can repeat an underscore with the .repeat string method. Don't forget to update i afterwards, so it keeps pointing to the currently processed character (which moved forward).
So your code could work like this:
import java.lang.Math;
import java.util.HashMap;
import java.util.ArrayList;
public class Spacer {
public static void main (String args[]) {
System.out.println("QQ,2 = " + spacey("QQ", 2) + ", expected 4");
System.out.println("ABCA,2 = " + spacey("ABCA",2) + ", expected 4");
System.out.println("DEDEE,1 = " + spacey("DEDEE", 1) + ", expected 6");
System.out.println("JKJK,2 = " + spacey("JKJK", 2) + ", expected 5");
}
private static int spacey(String word, int spaces) {
HashMap<Character, Integer> hm = new HashMap<>();
for (int i=0; i<word.length(); i++) {
char letter = word.charAt(i);
if (hm.get(letter) == null) {
hm.put(letter, i);
} else {
int underscores = hm.get(letter) + spaces + 1 - i;
if (underscores > 0) { // Need to add underscores
word = word.substring(0, i) + "_".repeat(underscores) + word.substring(i);
i += underscores; // update i so it still points to the current character
}
hm.put(letter, i);
}
}
return word.length();
}
}

How to tokenize the string with and without delimiter in single split

Assume i have a single string content as follows
Input:
FTX+AAA+++201707141009UTC'
FTX+BBB+++201707141009UTC'
FTX+CCC+++201707141009UTC?:??'
PISCO US LTS;?:V.D??'
SOUZA?:GB?:GB'
FTX+ZZZ+++201707141009UTC'
Expected Output:
Number of segments: 4
Input:
FTX+AAA+++201707141009UTC'
FTX+CCC+++201707141009UTC?:??'
PISCO US LTS;?:V.D??'
FTX+ZZZ+++201707141009UTC'
Expected Output:
Number of segments: 3
Basically i want to consider as same line when the delimiter ' comes with a question mark. The line delimiter is '
How to tokenize and get the count the segments in Java ???
Thanks in advance.

You can use a negative lookbehind in a regex:
String input = "FTX+AAA+++201707141009UTC'\n"
+ " FTX+BBB+++201707141009UTC'\n"
+ " FTX+CCC+++201707141009UTC?:??'\n"
+ " PISCO US LTS;?:V.D??' \n"
+ " SOUZA?:GB?:GB'\n"
+ " FTX+ZZZ+++201707141009UTC'";
String[] tokens = input.split("(?<!\\?)'\\s*");
System.out.println(tokens.length);
4
But, in the second example I would expect two segments, not three...

Another alternative to the above - but again demonstrating that the second example you post may be wrong because the third line ends with a ?' which, by your definition should not be a break.
public void test() {
test("FTX+AAA+++201707141009UTC'" +
"FTX+BBB+++201707141009UTC'" +
"FTX+CCC+++201707141009UTC?:??'" +
"PISCO US LTS;?:V.D??'" +
"SOUZA?:GB?:GB'" +
"FTX+ZZZ+++201707141009UTC'");
test("FTX+AAA+++201707141009UTC'" +
"FTX+CCC+++201707141009UTC?:??'" +
"PISCO US LTS;?:V.D??'" +
"FTX+ZZZ+++201707141009UTC'");
}
private void test(String s) {
String[] split = s.split("(?<!\\?)'");
System.out.println(split.length+"->"+Arrays.toString(split));
}
prints
4->[FTX+AAA+++201707141009UTC, FTX+BBB+++201707141009UTC, FTX+CCC+++201707141009UTC?:??'PISCO US LTS;?:V.D??'SOUZA?:GB?:GB, FTX+ZZZ+++201707141009UTC]
2->[FTX+AAA+++201707141009UTC, FTX+CCC+++201707141009UTC?:??'PISCO US LTS;?:V.D??'FTX+ZZZ+++201707141009UTC]

I think what he/she want is this:
String a = "FTX+AAA+++201707141009UTC'"
+ "FTX+BBB+++201707141009UTC'"
+ "FTX+CCC+++201707141009UTC?:??'"
+ "PISCO US LTS;?:V.D??' "
+ "SOUZA?:GB?:GB'"
+ "FTX+ZZZ+++201707141009UTC'";
String result[] = a.split("'");
List<String> stringList = new ArrayList<String>(Arrays.asList(result));
for (int i = 0; i < stringList.size(); i++) {
if (!stringList.get(i).startsWith("FTX") && i != 0) {
stringList.set(i-1, stringList.get(i-1) + stringList.get(i));
stringList.remove(i);
i--;
}
}
for (int j = 0; j < stringList.size(); j++) {
System.out.println(stringList.get(j));
}
FTX+AAA+++201707141009UTC
FTX+BBB+++201707141009UTC
FTX+CCC+++201707141009UTC?:??PISCO US LTS;?:V.D?? SOUZA?:GB?:GB
FTX+ZZZ+++201707141009UTC

Extra + signs on my program

I wrote a program for my Computer Science class where it reads a file and imports the data and then just adds the numbers but it seems to be adding an extra addition sign.
import java.io.*; //necessary for File and IOException
import java.util.*; //necessary for Scanner
public class Tester
{
public static void main( String args[] ) throws IOException
{
Scanner sf = new Scanner(new File("/Volumes/DVLUP Flash/Numbers.txt"));
int maxIndx = -1; //-1 so when we increment below, the first index is 0
String text[] = new String[1000]; //To be safe, declare more than we
while(sf.hasNext( ))
{
maxIndx++;
text[maxIndx] = sf.nextLine( );
//System.out.println(text[maxIndx]); //Remove rem for testing
}
sf.close();
for(int j =0; j <= maxIndx; j++)
{
Scanner sc = new Scanner(text[j]);
}
String answer = ""; //We will accumulate the answer string here.
int sum; //accumulates sum of integers
for(int j = 0; j <= maxIndx; j++)
{
Scanner sc = new Scanner(text[j]);
sum = 0;
answer = "";
while(sc.hasNext())
{
int i = sc.nextInt();
answer = answer + i + " + ";
sum = sum + i;
}
//sc.next();
answer = answer + " = " + sum;
System.out.println(answer);
}
}
}
The output is
12 + 10 + 3 + 5 + = 30
18 + 1 + 5 + 92 + 6 + 8 + = 130
2 + 9 + 3 + 22 + 4 + 11 + 7 + = 58
There's an extra after the last number, how do I fix that?

After the last iteration you are having an "extra" plus sign because that´s the way you are printing it. You are ending the String with a + as it can be seen in your while loop.
to change it either add the + before the value as
if(sc.hasNext()) {
int i = sc.nextInt();
answer = i + "";
sum += i;
while(sc.hasNext())
{
i = sc.nextInt();
answer = answer + " + " + i;
sum = sum + i;
}
}
Or if you use Java 8 you could use the StringJoiner as
StringJoiner joiner = new StringJoiner(" + ");
while(sc.hasNext())
{
i = sc.nextInt();
// This automaticly includes a " + " between the values.
joiner.add(String.valueOf(i));
sum = sum + i;
}

After
while(sc.hasNext())
{
int i = sc.nextInt();
answer = answer + i + " + ";
sum = sum + i;
}
put
answer = answer.substring(0, answer.length()-1);

One option would be to conditionally prepend a plus sign before appending each number in any case other than the first number:
answer = "";
while(sc.hasNext()) {
int i = sc.nextInt();
if (answer.length() > 0) {
answer += " + ";
}
answer = answer + i;
sum = sum + i;
}

NullPointer Exception Jcreator, Java

I am having an incredibly difficult time trying to figure out why I am getting this error.
When I use a driver file to test the program it fails horribly.
Here's my code:
import java.util.Scanner;
import java.lang.Math.*;
public class Histogram
{
private int[] arrayData;
private int[] arrayRange;
private final int LOW = 1;
private final int HIGH = 100;
public Histogram()
{
int[] arrayData = new int[11];
}
public void getInput()
{
int[] arrayRange = new int[11];
for(int count = 1; count < arrayRange.length; count++)
{
arrayRange[count] = count * 10;
}
Scanner input = new Scanner(System.in);
System.out.println("Enter numbers from 1 to 100, Type -999 to quit.");
int nextNumb = input.nextInt();
while(nextNumb != -999)
{
if(nextNumb >= LOW && nextNumb <= HIGH)
{
for(int i = 0; i <= arrayRange.length; i++)
{
if(nextNumb > arrayRange[i] && nextNumb <= arrayRange[i+1])
arrayData[i]++;
}
nextNumb = input.nextInt();
}
else arrayData[10]++;
nextNumb = input.nextInt();
}
}
public String starPrint(double count)
{
String star = "";
count = (Math.round(count) / 5);
for(int i = 1; i <= count; i++)
{
star = star + "*";
}
return star;
}
public String toString()
{
String results = " Range | Histogram" + "\n";
results = results + "1 - 10 | " + starPrint(arrayData[0]) + "\n";
results = results + "11 - 20 | " + starPrint(arrayData[1]) + "\n";
results = results + "21 - 30 | " + starPrint(arrayData[2]) + "\n";
results = results + "31 - 40 | " + starPrint(arrayData[3]) + "\n";
results = results + "41 - 50 | " + starPrint(arrayData[4]) + "\n";
results = results + "51 - 60 | " + starPrint(arrayData[5]) + "\n";
results = results + "61 - 70 | " + starPrint(arrayData[6]) + "\n";
results = results + "71 - 80 | " + starPrint(arrayData[7]) + "\n";
results = results + "81 - 90 | " + starPrint(arrayData[8]) + "\n";
results = results + "91 - 100 | " + starPrint(arrayData[9]) + "\n";
results = results + "Outliers: " + starPrint(arrayData[10]) + "\n";
return results;
}
}
I believe that the problem is in my getInput method
right here to be precise:
if(nextNumb > arrayRange[i] && nextNumb <= arrayRange[i+1])
arrayData[i]++;
I have no idea what's wrong with it though I am a beginner programmer and couldn't find a solution to this particular problem.
Thanks for any help you're able to give!

public Histogram()
{
int[] arrayData = new int[11];
}
You're shadowing your arrayData field in the constructor. This is creating a local variable with the same name as your class's arrayData field, initializing it, then immediately discarding it. When you try to use the field later in your code, it's null. Get rid of the int[] part.
Note that your next exception will be an ArrayIndexOutOfBoundsException ... you should look at your loop ;)

this: for(int i = 0; i <= arrayRange.length; i++)
wont work since you are trying to access arrayRange[i] and arrayRange[i+1]
which dont exists for i = arrayRange.length-1 and further
so change it to:
for(int i = 0; i < arrayRange.length-1; i++)

NoSuchElementException reading/ scanning input

Here is the main problem:
java.util.NoSuchElementException: No line found
at java.util.Scanner.nextLine(Unknown Source)
at ExamAnalysis.main(ExamAnalysis.java:21)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:271)
The program compiles and runs. It's just that I am either getting the java.util.NoSuchElementException along with my five jother errors with (answer.charAt(i) == char) near the bottom. Here is my program:
import java.io.*;
import java.util.Scanner;
class ExamAnalysis
{
public static void main(String [] args) throws FileNotFoundException
{
Scanner keyboard = new Scanner(System.in);
System.out.println("Please type the correct answers to the exam questions, one right after the other: ");
String answers = keyboard.nextLine();
System.out.println("Where is the file with all the student responses? ");
String responses = keyboard.nextLine();
Scanner read = new Scanner(new File(responses));
while (read.hasNextLine())
{
for (int i = 0; i <= 10; i++)
{
responses = read.nextLine();
int p = 1;
p += i;
System.out.println("Student " + p + " responses: " + responses.substring(0,10));
}
System.out.println("Thank you for the data on 9 students. Here's the analysis: ");
resultsByStudents(responses, answers);
analysis(responses);
}
}
public static void resultsByStudents(String responses, String answers)
{
System.out.println ("Student # Correct Incorrect Blank");
System.out.println ("~~~~~~~~~ ~~~~~~~ ~~~~~~~~~ ~~~~~");
int student = 0;
int correct = 0;
int incorrect = 0;
int blank = 0;
for (int i = 0; i <= 9; i++)
{
for (int j = 0; j <= responses.length(); j++)
{
if ((responses.charAt(j)) == answers.charAt(j))
correct++;
else if ((responses.charAt(j)) != answers.charAt(j))
incorrect++;
else
blank++;
}
System.out.println(student + " " + correct + " " + incorrect + " " + blank);
student++;
}
}
public static void analysis(String responses)
{
System.out.println("QUESTION ANALYSIS (* marks the correct response)");
System.out.println("~~~~~~~~~~~~~~~~~");
//stores the percentage of each choice chosen
double A = 0;
double B = 0;
double C = 0;
double D = 0;
double E = 0;
double X = 0;
// tallys every variable chosen per question
for (int i = 0; i <= 10; i++) // go through all the questions
{
for (int j = 0; j <= responses.charAt(i); j++) //go through all the student responses
{
// variable that are being tallied
int chooseA = 0;
int chooseB = 0;
int chooseC = 0;
int chooseD = 0;
int chooseE = 0;
int chooseBlank = 0;
//variables take percentage of choices that have been chosen from each student
A = chooseA/9;
B = chooseB/9;
C = chooseC/9;
D = chooseD/9;
E = chooseE/9;
X = chooseBlank/9;
// variables that will print the asterisk with certain character of correct answer
String a = "A";
String b = "B";
String c = "C";
String d = "D";
String e = "E";
String blank = "blank";
if (responses.charAt(j) == A)
chooseA++;
else if (responses.charAt(j) == B)
chooseB++;
else if (responses.charAt(j) == C)
chooseC++;
else if (responses.charAt(j) == D)
chooseD++;
else if (responses.charAt(j) == E)
chooseE++;
else
chooseBlank++;
System.out.println("Question #" + i);
if (answers.charAt(i) == 'A') a = "A*"; // answers cannot be resolved(I already made it a global variable in my main method.)
else if (answers.charAt(i) == 'B') b = "B*";// answers cannot be resolved
else if (answers.charAt(i) == 'C') c = "C*";// answers cannot be resolved
else if (answers.charAt(i) == 'D') d = "D*";// answers cannot be resolved
else if (answers.charAt(i) == 'E') e = "E*";// answers cannot be resolved
System.out.println(a + " " + b + " " + c + " " + d + " " + e + " " + blank);
System.out.println (chooseA + " " + chooseB + " " + chooseC + " " + chooseD + " " + chooseE + " " + chooseBlank );
System.out.println (A + " " + B + " " + C + " " + D + " " + E + " " + X);
}
}
}
}

while (read.hasNextLine())
{
for (int i = 0; i <= 10; i++)
{
responses = read.nextLine();
int p = 1;
p += i;
System.out.println("Student " + p + " responses: " + responses.substring(0,10));
}
System.out.println("Thank you for the data on 9 students. Here's the analysis: ");
resultsByStudents(responses, answers);
analysis(responses);
}
}
Your logic here is confusing you. read.nextLine(); "Advances this scanner past the current line and returns the input that was skipped. This method returns the rest of the current line, excluding any line separator at the end. The position is set to the beginning of the next line."
So you are saying, does it have a line? If so, read the next 10...well...11 lines, which isn't what you want. You don't know if there are 11 lines past this point. Don't know what that text file looks like, but you will want to restructure this part to either say, "While it has a next line", or "Read 11 lines"

Remove the for loop may resolve the issue. You are checking only once by using while(hasNextLine() ) but calling read.nextLine() 10 times in for loop.
for (int i = 0; i <= 10; i++)
{
responses = read.nextLine();
.......
}

int i = 0;
int numberOfStudents = 9;
while (i < numberOfStudents && read.hasNextLine()){
responses = read.nextLine();
i++;
System.out.println("Student " + i + " responses: " + responses.substring(0,10));
}
System.out.println("Thank you for the data on "+ numberOfStudents +" students. Here's the analysis: ");
resultsByStudents(responses, answers);
analysis(responses);
i < numberOfStudents : makes the required number of inserts
read.hasNextLine() : checks if there is input from console. If not the program waits for input.
for (int i = 0; i <= 10; i++)
count from 0 -> 10 = 11 students