Scanning different lines

[jamonathin]

I have a problem that requires me to read input from multiple lines. Problem is, i dont know how long each line is going to be.
For example, the line can be from 1-50 numbers long, and the number of columns is terminated by -1, where each number is seperated by a space.

So an sample input could be:

1 2 3 4 5 6 7
2 3 4 5 6 7 8
4 5 6 7 8 9 0
-1

or it could be:

2 3 4 5
4 5 6 7
-1

So how do i know when the user hits enter, and moves on to the next line?

[Monstrosity_]

jamonathin @ Mon Jan 29, 2007 11:41 am wrote:

So how do i know when the user hits enter, and moves on to the next line?

You get input. The input stream is buffered so you will not get anything until the user hits enter, then you get the line. You shouldn't be concerned about this since your are given an end of input delimiter. If you are asking for help on reading each number in until the delimiter is reached, I suggested you look over your input functions one more time.

HINT: new lines, tabs, spaces, etc are all white space.

[jamonathin]

But the thing is I dont know how many white spaces the user will enter, because i'm supposed to be storing each row in a 2d array. See, i'm supposed to end up sorting the second, third ... n'th rows to look like the first row inputted. If the user doesn't tell me how long/(how many white spaces) the row will be, how am I supposed to find this out?

Basically how would you store:

1 2 3 4 5
5 1 2 3 4
5 4 1 2 3

In a 2d array? When thats all that is given from the user? (not knowing the row will be 5 numbers long)

[Monstrosity_]

jamonathin wrote:

because i'm supposed to be storing each row in a 2d array. See, i'm supposed to end up sorting the second, third ... n'th rows to look like the first row inputted. If the user doesn't tell me how long/(how many white spaces) the row will be, how am I supposed to find this out?

Monstrosity_ wrote:

I suggested you look over your input functions one more time.

HINT: new lines, tabs, spaces, etc are all white space.

jamonathin wrote:

Basically how would you store

1 2 3 4 5
5 1 2 3 4
5 4 1 2 3

In a 2d array? When thats all that is given from the user? (not knowing the row will be 5 numbers long)

There's many ways.. you will need to decide if you want to set the upper limits (n,r) and have static memory for the array (array[n][r]) or dynamic memory that will grow as needed. You should stick with the former, then all you would need to do is read each value and store it as you go along from 0 to r-1. And also ensure no more then n lines are considered.

[OneOffDriveByPoster]

jamonathin @ Mon Jan 29, 2007 10:41 am wrote:

So how do i know when the user hits enter, and moves on to the next line?

There are many ways. Try using ungetc().

[Monstrosity_]

OneOffDriveByPoster @ Wed Jan 31, 2007 1:19 am wrote:

jamonathin @ Mon Jan 29, 2007 10:41 am wrote:

So how do i know when the user hits enter, and moves on to the next line?

There are many ways. Try using ungetc().

Mind elaborating? I don't understand how pushing a character back onto the stream would help here.

[OneOffDriveByPoster]

OneOffDriveByPoster @ Wed Jan 31, 2007 1:19 am wrote:

jamonathin @ Mon Jan 29, 2007 10:41 am wrote:

So how do i know when the user hits enter, and moves on to the next line?

There are many ways. Try using ungetc().

Monstrosity_ @ Wed Jan 31, 2007 8:04 am wrote:

Mind elaborating? I don't understand how pushing a character back onto the stream would help here.

One character look-ahead for finding '\n'.

[Monstrosity_]

OneOffDriveByPoster @ Wed Jan 31, 2007 12:19 pm wrote:

Monstrosity_ @ Wed Jan 31, 2007 8:04 am wrote:

Mind elaborating? I don't understand how pushing a character back onto the stream would help here.

One character look-ahead for finding '\n'.

Ok, I get looking for the new line but why would you want to push it back onto the stream? That just seems bass awkwards to me.

[OneOffDriveByPoster]

Monstrosity_ @ Wed Jan 31, 2007 1:15 pm wrote:

OneOffDriveByPoster @ Wed Jan 31, 2007 12:19 pm wrote:

One character look-ahead for finding '\n'.

Ok, I get looking for the new line but why would you want to push it back onto the stream? That just seems bass awkwards to me.

Not to push back the newline, but to push back a non-whitespace character if one is read.

[md]

*sigh* tried reading an entire line (with say getline()); then parsing that line?

It's a ridiculously easy problem and I am surprised that it hasn't been solved yet.

psudo:

y = 0 do         readline(&buffer)         x = 0         number == ""         for i = 0 to length(buffer)                 if !whitespace(buffer[i])                         concat(number, buffer[i])                 else                         array[x++,y] = atoi(number)                         number = ""         y++ while !eof

[Monstrosity_]

OneOffDriveByPoster @ Wed Jan 31, 2007 4:44 pm wrote:

Monstrosity_ @ Wed Jan 31, 2007 1:15 pm wrote:

OneOffDriveByPoster @ Wed Jan 31, 2007 12:19 pm wrote:

One character look-ahead for finding '\n'.

Ok, I get looking for the new line but why would you want to push it back onto the stream? That just seems bass awkwards to me.

Not to push back the newline, but to push back a non-whitespace character if one is read.

Doh! It was just me that was bass awkwards, I get ya now, thanks.

md wrote:

*sigh* tried reading an entire line (with say getline()); then parsing that line?

Reading the whole line is optional as OneOffDriveByPoster pointed out.

md wrote:

psudo:

y = 0 do         readline(&buffer)         x = 0         number == ""         for i = 0 to length(buffer)                 if !whitespace(buffer[i])                         concat(number, buffer[i])                 else                         array[x++,y] = atoi(number)                         number = ""         y++ while !eof

You psudo code mixes up two different ideas. If you grab the whole line, your are no longer worried about white space since you know where the new line is. If you decide to read the values from the stream, then you need to check white space so that you don't skip right over the new line character (which is what my hint was getting at). Also your psudo code is just flawed in general if values > 9 are allowed.

[md]

I think you'll find that my code does what it required; and it does it simply. Perhaps if you stopped to think about it...

[Monstrosity_]

md @ Wed Jan 31, 2007 8:16 pm wrote:

I think you'll find that my code does what it required; and it does it simply. Perhaps if you stopped to think about it...

psudo:

/* first iteration */ y = 0 do         readline(&buffer)  /* "12 13 14" */         x = 0         number = ""         for i = 0 to length(buffer) /* i = 0; length(buffer)=8;  */                 if !whitespace(buffer[i])                         concat(number, buffer[i]) /* number = "12 13 14" */                 else                         array[x++,y] = atoi(number) /* array[0][0] = 12 */                         number = ""         y++ while !eof /* second iteration */         for i = 0 to length(buffer) /* i=1 */                 if !whitespace(buffer[i])                         concat(number, buffer[i]) /* number = "2 13 14" */                 else                         array[x++,y] = atoi(number) /* array[1][0] = 2 */                         number = ""         y++ while !eof /* last iteration */         for i = 0 to length(buffer) /* i=8 */                 if !whitespace(buffer[i])                         concat(number, buffer[i]) /* number = "" */                 else                         array[x++,y] = atoi(number) /* array[6][0] = 0 */                         number = ""         y++

Given "12 13 14" your code should read in {12, 2, 13, 3, 14, 4, 0}? If I missed something feel free to correct me.

[OneOffDriveByPoster]

md @ Wed Jan 31, 2007 7:16 pm wrote:

I think you'll find that my code does what it required; and it does it simply. Perhaps if you stopped to think about it...

Okay, yes, no leading or trailing whitespace and one space between each character. I don't like the buffer though. I guess anything else could be explained by it being pseudocode.

[md]

Monstrosity_ I am not at all sure what yoru comments mean... but from what I gather you are wrong.

As I'm sure wtd has mentioned before being able to trace code is a key part of programming... so try again and I'll tell you if your closer.

[edit] to clarify contat takes a string and a character and adds teh character to the string. whitespace returns true if hte passed character is a whitespace character. Those seem to be the things that people don't understand...