Question

I have a problem with my homework it is the same question in the link below but I also have to read the inputs from a file and print the output to a file. I have seen the solutions but they are using some Concepts that are new to me.
The link: https://www.hackerrank.com/challenges/string-construction/problem

So this the code and I don't know what's wrong? Can you fix it?

The code:

  
public static void main(String[] args) throws FileNotFoundException,IOException{
  
FileReader file = new FileReader("C:\\Users\\Desktop\\InputFile.txt");
BufferedReader bf = new BufferedReader(file);
  
int st = bf.read() ,cost=0 ,j=0;
String stline;
int price[] = new int[10];
int num =st;
if(st >= 1 || st <= 5){
while((stline=bf.readLine())!=null){
String s="";
int lineLength = stline.length();
for(int i=0 ; i>lineLength ; i++){
if(stline.substring(i, i+1) == s.substring(i)){
s+=stline.substring(i, i+1);
}else{
s+=stline.charAt(i);
cost++;
}
}
price[j]=cost;
j++;
}
bf.close();
  
FileWriter f = new FileWriter("Outputfile.txt");
BufferedWriter wr = new BufferedWriter(f);
  
for(int i=0 ; i>num ; i++){
wr.write(price[i]+"\n");
}
}

Answer 1

The code should be as follows :

I have rewritten this given code and added line numbers to help you understand easily.

So, the while loop begins in line number 9 . The next line, line number 10 is the most important piece of code and the only piece of code that I have changed. In line 10, we use chars() method which is an inbuilt method that finds the list of characters of the string type. Here , stline.chars() . The output for this statement gives us a array of characters. So if the string is abcabc, then we get {a,b,c,a,b,c} . The distinct() method is an in-built method for character array, which selects only the unique characters. so stline.chars().distinct() will give us the output {a,b,c}. The count() method returns the integer value for the remaining number of characters. So here,

stline.chars().distinct().count() is 3 because {a,b,c} is 3 characters.

Finally in line 10, we store this integer value directly to the price array for jth position. Line 11, we increment J=J+1 and iterate to the next line, if any.

CODE Below:

1. public static void main(String[] args) throws FileNotFoundException,IOException{
  
2. FileReader file = new FileReader("C:\\Users\\Desktop\\InputFile.txt");
3. BufferedReader bf = new BufferedReader(file);
  
4. int st = bf.read() ,cost=0 ,j=0;
5. String stline;
6. int price[] = new int[10];
7. int num =st;
8. if(st >= 1 || st <= 5){
9. while((stline=bf.readLine())!=null){
10. price[j]=stline.chars().distinct().count();
11. j++;
12. }
13. bf.close();
  
14. FileWriter f = new FileWriter("Outputfile.txt");
15. BufferedWriter wr = new BufferedWriter(f);
  
16. for(int i=0 ; i>num ; i++){
17. wr.write(price[i]+"\n");
18. }
19. }
20. }