My head is about to explode!

[Abdulmalik Malik]

Hi guys, how is it going?!

In short, I've got a cipher code, and all I need to do is to:

1-count the occurrences for each letter
2-replace the most frequent letter with 'E', the second with 'T' and so on.

Fairly simple!

However, what I have done is :

import java.util.*;

public class decryption {


 public static void main (String str[])
	{	
                int[] freq= new int[26];
		String n = "ZYEMOUSOUSIZWYIXOKSOTSUSIRMHTSVSIBHTSOTNTZYERYGIHRSOQIYDIOXRMORORROBNTBHQMSI";

char [] cyp = n.toCharArray();// in order to deal with each letter individually when it comes to the replacement step

char Alpha[] = {
     'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
     //The English alphabet 

	for (int i=0;i<n.length();i++)//for counting occurrences for each letter
			{
               int index=n.charAt(i)-'A';
			 freq[index]++;			
			}
for(int i=0;i<26;i++)// To sort in an ascending order
	for(int j=i;j<26;j++)
		if(freq[i]>freq[j])
		{
		  int temp=freq[i];	
		  freq[i]=freq[j];
		  freq[j]=temp;
		}

	for (int i=0;i<26;i++)
	System.out.println(Alpha[i]+"-->"+freq[i]);


}
}    

so, my problem is that once I finish counting how many times each letter appeared, I don't know what to do next because of the changing of 'freq' array, which's got each index corresponds to an alphabetic one (0,A),(1,B)...and so on

please enlighten me to improve this code

[Miklos Szeles]

Hi,
Welcome to javaranch. This prolem was discussed in the forum several times, so I advice you to do a search on the subject here in the forum.
Think a little bit about the sorting part. You stored the occurence count for all the letters in your array. You know that freq[0] belongs to Alpha[0], freq[1] belongs to Alpha[1], ....
After counting you reorder the freq array. You missed one thing here. What do you want to achieve by reordering the array? Think about it and you will see what I'm talking about.

[Abdulmalik Malik]

Thanks Miklos

I believe that you're talking about I have missed each letter number of occurrences !?
This is my nightmare that I could do!

[Miklos Szeles]

I mean, you sort the freq array to order the letters based on the count of their occurences which is right. But you just mix up the freq array and forgot to order the alphabet according to that.

[Abdulmalik Malik]

WOW! I never thought of that!
I'll have a go, thank you

[Abdulmalik Malik]

I give up

any further hints?

[Miklos Szeles]

You give up really easy. Forget about Java, just concentrate on the algorithm. Write down the algorithm, and when it's okay you can start to implement it in Java. We can help with that,but we won't give the soultion instead of you;)

[Campbell Ritchie]

And if you want answers, in future please note this FAQ.

[Abdulmalik Malik]

I really appreciate your collaboration, and believe me I'm not looking for a ready-solution ..and to show my good intentions let me tell you what I am thinking about,algorithm-wise not java:

1-Create a two-dimensional array arr[26][2], the first column is for holding indices from 0-25, and the other one is holding the frequencies for each letter taking the values from "freq" array ,e.g: a[0][0]=0-->A & a[0][1]= 10 times of occurrences

2-After that we sort the 2-dimensional array according to the 2nd column which holds the occurrences number, so we still hold the index for every letter,and easily we know where the 'A' went and other letters

3-Now I got lost!!

[Abdulmalik Malik]

Campbell Ritchie wrote:And if you want answers, in future please note this FAQ.

Sorry, cheer up mate

[Abdulmalik Malik]

This what I could come up with! it didn't work though!

import java.util.*;

public class decrypt {

public static void main (String str[])
	{	int[] freq= new int[26];
		String n = "ZYEMOUSOUSIZWYIXOKSOTZQSOBSYLSWDKHTMOWARMSKSRRN";
char [] cyp = n.toCharArray();
char Alpha[] = {'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};//The English alphabet 
int [] TAlpha= new int[]{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};


	for (int i=0;i<n.length();i++)
			{
               int index=n.charAt(i)-'A';
			 freq[index]++;			
			}
System.out.println("This is before sorting");
int[][] arr=new int[26][2];

	for (int i=0;i<26;i++)
		arr[i][0]=i;
	
	for (int i=0;i<26;i++)
		arr[i][1]=freq[i];

	for (int i=0;i<26;i++)
System.out.println(Alpha[i]+"-->"+arr[i][0]+"|"+arr[i][1]);
///////////////////////////////////////
System.out.println("This is after sorting");
for(int i=0;i<26;i++)
	for(int j=i;j<26;j++)
		if(arr[i][1]>arr[j][1])
		{
		  int temp= arr[i][1];	
		  arr[i][1] = arr[j][1];
		  arr[j][1]=temp;		 
		}
	for (int i=0;i<26;i++)
System.out.println(Alpha[i]+"-->"+arr[i][0]+"|"+arr[i][1]);

}
}

[Campbell Ritchie]

Please have a look at the administrative private message I sent a minute or so ago.

[Pedantic mode]There is no such thing as a 2D array in Java. You only get arrays of arrays, which are more versatile[/Pedantic mode]

You only need one array for counting frequencies, if you are using arrays. No need for two arrays. You simply need a frequency array, and you can increment the elements as you pass the letters. That bit is really easy. You probably don't need the ABCD... array either.

[Abdulmalik Malik]

Campbell Ritchie wrote:Please have a look at the administrative private message I sent a minute or so ago.

[Pedantic mode]There is no such thing as a 2D array in Java. You only get arrays of arrays, which are more versatile[/Pedantic mode]

You only need one array for counting frequencies, if you are using arrays. No need for two arrays. You simply need a frequency array, and you can increment the elements as you pass the letters. That bit is really easy. You probably don't need the ABCD... array either.

Thanks a lot, the counting bit is easy, but my problem still in how I can hold the index of each frequency! in order to replace its corresponding letter

[Campbell Ritchie]

I take your point. You need some way to link letters to frequencies.

Set up a class which incorporates a letter, a frequency and a replacement letter. Put those in the array from A to Z. Remember a char is not a character at all, despite what people say. It is a number. You can do arithmetic on it. Try this:

System.out.println('z' - 'a');
System.out.println('z' - 'a' + 1);

So you can use each letter to access the array and call its increment() method.
Make your class implement the Comparable interface, and simply subtract the two frequencies in the compareTo() method.
Then set the replacement character after sorting, and comparison with the frequencies. According to this Oxford English Dictionary website, that is EARIOTNSLCUDPMHGBFYWKVXZJQ. But you have been given a different set of frequencies, which you had best use.
Then use that replacement in your original String.

[Abdulmalik Malik]

Campbell Ritchie wrote:I take your point. You need some way to link letters to frequencies.

Set up a class which incorporates a letter, a frequency and a replacement letter. Put those in the array from A to Z. Remember a char is not a character at all, despite what people say. It is a number. You can do arithmetic on it. Try this:

System.out.println('z' - 'a');
System.out.println('z' - 'a' + 1);

So you can use each letter to access the array and call its increment() method.
Make your class implement the Comparable interface, and simply subtract the two frequencies in the compareTo() method.
Then set the replacement character after sorting, and comparison with the frequencies. According to this Oxford English Dictionary website, that is EARIOTNSLCUDPMHGBFYWKVXZJQ. But you have been given a different set of frequencies, which you had best use.
Then use that replacement in your original String.

I really appreciate your hints, but I still can't do it!
Especially I don't know what to compare with each other!?

[Campbell Ritchie]

I tried it last night with both the frequency tables on that Oxford website, and got a decrypted output . . . and couldn't understand it

If you want to get the index of your 26-element array, try myLetters['z' - 'a'].
Create a simple method which demonstrates an array like that.
Then go through your coded String, and for each of the letters, increment the count in your array. You can even iterate through the array like this

for (int i = 0; i < myArray.length; i++)
{
    System.out.printf("There are %d instances of the letter %c%n",
            myArray[i], (char)(i + 'A'));
}// end for

See if you can get that bit working. See whether that helps at all. Note you can use upper-case and lower-case versions of that for loop.

[Abdulmalik Malik]

Campbell Ritchie wrote:I tried it last night with both the frequency tables on that Oxford website, and got a decrypted output . . . and couldn't understand it

If you want to get the index of your 26-element array, try myLetters['z' - 'a'].
Create a simple method which demonstrates an array like that.
Then go through your coded String, and for each of the letters, increment the count in your array. You can even iterate through the array like this

for (int i = 0; i < myArray.length; i++)
{
    System.out.printf("There are %d instances of the letter %c%n",
            myArray[i], (char)(i + 'A'));
}// end for

See if you can get that bit working. See whether that helps at all. Note you can use upper-case and lower-case versions of that for loop.

If you really interested in knowing the whole thing , here you go:
ZYEMOUSOUSIZWYIXOKSOTZQSOBSYLSWDKHTMOWARMSKSRRSILISFESWBHSTOISQISRRZWSOIRYRMSOUSIODSTLYISWDKHTMOWAWYEWBYXXYWSWDKHTMGYIATOISQISTSWRRMSYRMSIRSVRTGHKKWYRJSTYSOTZOWAXOZJSMOIARYAYJISONHWDRMHTBHQMSIJZMOWATMYEKAWYRJSAHLLHBEKRRYAYMYGSUSIRMHTSVSIBHTSOTNTZYERYGIHRSOQIYDIOXRMORORROBNTBHQMSITOERYXORHBOKKZOWAJISONTRMSXGHRMYEROETSIMOUHWDRYPEXQHWOWAXONSOBMOWDSOTHXQKSJIERSLYIBSOQQIYOBMHTWYRWSBSTTOIHKZRMSWHBSTRGOZRYAYWSRMHTRMSRIHBNRYAYHWDRMHTGHKKJSRYASRSBRGMSWRMSTEJTRHRERHYWHTWYRIHDMROWARYLHWAOJSRRSIYWSETHWDRMSLISFESWBHSTRYDEHASZYEDYYAKEBN

and thanks for the help, I'll try it

[Henry Wong]

for(int i=0;i<26;i++)   
    for(int j=i;j<26;j++)   
        if(arr[i][1]>arr[j][1])   
        {   
          int temp= arr[i][1];     
          arr[i][1] = arr[j][1];   
          arr[j][1]=temp;           
        }   

When you swap the freqs, shouldn't you swap the letters too? After all, the letter and freqs should stay together right?

Henry

[Abdulmalik Malik]

Henry Wong wrote:

for(int i=0;i<26;i++)   
    for(int j=i;j<26;j++)   
        if(arr[i][1]>arr[j][1])   
        {   
          int temp= arr[i][1];     
          arr[i][1] = arr[j][1];   
          arr[j][1]=temp;           
        }   

When you swap the freqs, shouldn't you swap the letters too? After all, the letter and freqs should stay together right?

Henry

Thanks a lot, I should not miss that!

[lisa broker]

I just wanna say one thing, programming require patient a lot, keep going

[Abdulmalik Malik]

lisa broker wrote:I just wanna say one thing, programming require patient a lot, keep going

Exactly, and this what I lack, I'm afraid!
But by staying in touch, with people as such, I should become patient very much!