Java programming question

[dingo]

I am writing a program using arrays and am having a bit of trouble.
The task is to accept integer inputs from the user and put them in an array.....but that part is not the prob.
Then I need to count the occurences of each integer and print them to the screen....so for example if the user enters 1, 3, 44, 42, 21, 21, 3, 8 then it would print out:

1 1
3 2
8 1
21 2
42 1
44 1

I can't figure out how to count the number of times each int has been entered...can anybody give me any ideas?

[stracing]

int input[100]; /initialise arrays/
int freq[];
int count;

..... /get user input, store in array. you've done this bit/

for (count = 0; count <= "input array size(find the array size)" -1; answer++)
++freq[input[count]];

.../then print out your arrays/

[dingo]

Thanks so much stracing, I appreciate the help.
I gave that a go and it seems to work sort of, but not auite right.
I tried it with an array size of 6, and when I enter six 1's...then I would expect it to print out:

1 6

but instead it prints out 0 6 0 0 0 0...so something is a little off...but not sure what.
Also I changed 'answer++' in the for loop to count++, as I assume thats what you meant.

[graywolf624]

One suggestion would be a hash table.
IF your not familiar with that then:

/loop through and add user values to your array
/create a 2 dimensional array of the same size. 0 out the whole thing.
/loop till array.getsize()-1 with a for loop.
/get the first value in the array.
/loop through and count and remove from the array all occurances of that value.
/place the value you were searching for in the first dimension in that 2d array. place the count in the second.

/loop through 2 d array finding the values in whatever order you wish.. and print both the occurance and value out.



If you want I can right this in java as well, but Id prefer you actually do some of the work.

[dingo]

Thanks for the suggestion graywolf, but it needs to be implemented using only a single (preferably) array...and no hash tables since I haven't learnt about them yet.

[graywolf624]

ok fair enough..

/create two 1 d arrays
/loop through add all values of array.

/loop till array.getsize()-1 with a for loop.
/get the first value in the array.
/loop through and count and remove from the array all occurances of that value except the first one.
/place the count in the second. next to the first existance of the value you were searching for.
/loop through and where value in the second array doesnt =0 and value in first array is in order you want.. print them both out.

[DeMoN]

Originally Posted by stracing int input[100]; /initialise arrays/ int freq[]; int count; ..... /get user input, store in array. you've done this bit/ for (count = 0; count <= "input array size(find the array size)" -1; answer++) ++freq[input[count]]; .../then print out your arrays/

i would do it...

int input[100]; /initialise arrays/
int count;

then do a for loop to add the numbers to the array input, each time you add a number to the array do a count++

once the adding is complete, count should have a value equal to the numbers inputed to the array

now:

int freq[count] = 0; // will make a new array with the size = to count and make them all 0

for (int i=0 ; i < count ; i++) {
for (int j=0 ; j < count ; j++) {
if (input[i] == input[j]) freq[i]++;
}
}

then print array input and arry freq with another loop

for (int i = 0 ; i < count ; i++) {
System.out.println(input[i] + " " + input[j]);
}

[stracing]

with my code you needed to get rid of the zeroes. then find a way to match your two arrays. so the print out is kinda right. remember arrays begin at "zero" not "one". thats why the 6 is the second element because you wanted to print the amount of "ones".

sorry i couldn't get it to fully work for you. to be honest i haven't done java programming for few years now. i'm just rehashing what i've remembered

but graywlfs second suggestion was what i was getting at

[stracing]

i wish i had the net during my days of programming. i could just ask for solutions off ppl

[AlienDB7]

DeMoN, I haven't test out your code but I think your code will get duplicate results. For example, if the user enters 1, 3, 4, 1 then the output will show the count for "1" twice. Not sure if you're familiar with 2 dimensional array but you can have a 2D array storing the # and the count. One simple and dirty solution would be to integrate the user input and counting together

1. Ask for user input
2. Search for the user input # in the array
3. If found then increment the count, else insert # to end of array with count = 1
4. Go to step 2

The code should be pretty simple, you don't even need multiple arrays. Good luck.

[graywolf624]

Not sure if you're familiar with 2 dimensional array but you can have a 2D array storing the # and the count

He already shot down my solution on that one... see above.

[dingo]

Thanks for all the help guys, I will try out the new solutions later tonight.

[DeMoN]

int temp; // holds the number typed by user
int input[100] = -1; // assuming -1 is not valid input
int freq[100] = 0;
int count;
bool add; // if the number isnt found, it adds it

now you do a for loop to test if the value already exists
while ( (temp != null) && (temp >= 0) ) {
add = true; // always set tu ture and if it stays this way, we add
for (int i = count ; i >= 0 ; i--) {
if (temp == input[i]) { freq[i]++; add = false;}
}
if (add) { input[i] = temp; count++;}
}

ok this one should work. hope you understand it. Now i go sleep.

[DeMoN]

this is doing the right stuff, but you have to play a little bit more with it


import java.io.*;

public class Lab04Test1 {
private static BufferedReader stdin = new BufferedReader( new InputStreamReader( System.in ) );

public static void main ( String [] args ) throws IOException {
int SIZE = 100;
String input;
int[] intput = new int[SIZE];
int[] freq = new int[SIZE];
int count=0;
int temp;
boolean add;

for (int i=0 ; i<SIZE ; i++) {
intput[i] = -1;
freq[i] = 0;
}

System.out.println( "Type some data for the program: " );
while (true) {
input = stdin.readLine();
temp = Integer.parseInt(input);
if (temp == -1) {
add = false;
break;
}

add = true; // always set tu ture and if it stays this way, we add
int i;
for (i = count-1 ; i >= 0 ; i--) {
if (temp == intput[i]) {
freq[count-1]++;
add = false;
break;
}
}
if (add) {
intput[count] = temp;
freq[count]++;
count++;
}
}
System.out.println("End");
for (int i=0 ; i<count ; i++) {
System.out.println(intput[i] + " " + freq[i]);
}
}
}

[dingo]

Thanks DeMon, and all the other guys. I thought you said you were going to sleep, but an hour later you posted again.
I haven't found the time to try them all out, but will let you know how I go.