Help with 2d arrays

Hi there
i need some help manipulating a 2d array.
For example
say i have an 2d array

Code:

int array[20][21]={{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, //Crop this {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, // Crop this {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, // Crop this {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, // Crop this {0,0,0,0,0,1,0,1,1,1,1,0,0,1,0,1,0,1,0,1,0}, {0,0,1,0,1,0,1,0,1,0,0,0,1,0,0,1,0,0,1,0,1}, {1,0,0,1,0,1,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0}, {0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0}, {1,0,1,0,1,0,0,1,0,0,0,1,0,0,0,1,0,1,1,0,0}, {0,0,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0}, {0,1,0,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1}, {1,1,0,1,0,1,0,0,0,1,0,0,0,1,0,0,1,0,0,1,0}, {0,0,1,1,0,1,0,0,0,0,1,0,0,1,0,0,1,0,0,0,1}, {1,0,1,0,1,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1}, {1,0,0,1,0,0,0,1,0,0,1,0,1,0,0,0,1,0,1,0,0}, {1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, // Crop this {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, // Crop this {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}}; // Crop this

I want to crop any 2d array like the one above matrix i get so that the matrix that start with with a column that has 1's in it. and end with a column that has one int it. ie if it has a column with all zeros at the begining or end it should crop it out..
to provide an 2d array like the following:

Code:

{{0,0,0,0,0,1,0,1,1,1,1,0,0,1,0,1,0,1,0,1,0}, {0,0,1,0,1,0,1,0,1,0,0,0,1,0,0,1,0,0,1,0,1}, {1,0,0,1,0,1,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0}, {0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0}, {1,0,1,0,1,0,0,1,0,0,0,1,0,0,0,1,0,1,1,0,0}, {0,0,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0}, {0,1,0,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1}, {1,1,0,1,0,1,0,0,0,1,0,0,0,1,0,0,1,0,0,1,0}, {0,0,1,1,0,1,0,0,0,0,1,0,0,1,0,0,1,0,0,0,1}, {1,0,1,0,1,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1}, {1,0,0,1,0,0,0,1,0,0,1,0,1,0,0,0,1,0,1,0,0}, {1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1}};

help me please...
thanks cheer

Please do NOT put comments inside the code tags - ONLY put the code inside the code tags.
And why not just copy data into a new array then?

sorry about the comments

[/code]
Hi well technically i can't because i don't know the size of the array i'm using.. i will jst have to open the file they give me and the program will have to do that for me.
[code]

It's good you listened to Elysia about the code tags :)... er not.

A simple loop that traverses the array, and if you didn't find a non-zero don't add it to the 2nd array...

Quote:

Originally Posted by zacs7

It's good you listened to Elysia about the code tags :)... er not.

A simple loop that traverses the array, and if you didn't find a non-zero don't add it to the 2nd array...

Hi the not following about traverse, i'm just a beginner so can you go though it with me...
please.

thanks in advance

Oh but it is, how are you going to 'see' what's in the array without traversing it?

By traversing the array he basically means going through each element reading the content.

You could then have four variables: x_start, x_end, y_start, and y_end. When reading the array you would want to find these four points.

When you are finished reading you could then crop the array to everything between these co-ordinates.

I read his post a little differently. I thought he wanted to save just the rows that contained at least one value of 1, in them.

Code:

for(row = 0, j = 0; row < MaxRowsInOriginalArray; row++) { goodrow = 0; for(col = 0; col < MaxColsInOriginalArray; col++) { if(OriginalArray[row][col] == 1) goodrow = 1; //mark this row to be saved break; } if(goodrow == 1) { for each col - as above. NoZeroArray[j++][col] = OriginalArray[row][col]; } }

To work like this, the NoZeroArray must have the same number of columns as the OriginalArray has. It may need the same number of rows, IF the OriginalArray has no rows that are all zero's.

thank bro you got the idea i was impleamenting

Quote:

Originally Posted by Adak

I read his post a little differently. I thought he wanted to save just the rows that contained at least one value of 1, in them.

Code:

for(row = 0, j = 0; row < MaxRowsInOriginalArray; row++) { goodrow = 0; for(col = 0; col < MaxColsInOriginalArray; col++) { if(OriginalArray[row][col] == 1) goodrow = 1; //mark this row to be saved break; } if(goodrow == 1) { for each col - as above. NoZeroArray[j++][col] = OriginalArray[row][col]; } }

To work like this, the NoZeroArray must have the same number of columns as the OriginalArray has. It may need the same number of rows, IF the OriginalArray has no rows that are all zero's.

what is wrong with my code
it is print out junk values for some reason

Code:

#include <stdio.h> int main(int argc,char *argv[]){ int row; int col; int goodrow=0; int j; int array[20][21]={{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,1,0,1,1,1,1,0,0,1,0,1,0,1,0,1,0}, {0,0,1,0,1,0,1,0,1,0,0,0,1,0,0,1,0,0,1,0,1}, {1,0,0,1,0,1,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0}, {0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0}, {1,0,1,0,1,0,0,1,0,0,0,1,0,0,0,1,0,1,1,0,0}, {0,0,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0}, {0,1,0,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1}, {1,1,0,1,0,1,0,0,0,1,0,0,0,1,0,0,1,0,0,1,0}, {0,0,1,1,0,1,0,0,0,0,1,0,0,1,0,0,1,0,0,0,1}, {1,0,1,0,1,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1}, {1,0,0,1,0,0,0,1,0,0,1,0,1,0,0,0,1,0,1,0,0}, {1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}}; int resultarray[14][20]={}; for(row = 0, j = 0; row < 20; row++) { goodrow = 0; for(col = 0; col < 21; col++) { if(array[row][col] == 1) goodrow = 1; //mark this row to be saved break; } if(goodrow == 1) { for (col=0;col<21;col++) { resultarray[j++][col] = array[row][col]; } } } for(row=0;row<j;row++){ for(col=0;col<21;col++){ printf("%d",resultarray[row][col]); } printf("\n"); } return 0; }

cheer bro

You students nowadays, you expect code I post to be close to actually working! :)

Code:

#include <stdio.h> int main(int argc,char *argv[]) { int row, col, j; int goodrow=0; int array[20][21]={{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,1,0,1,1,1,1,0,0,1,0,1,0,1,0,1,0}, {0,0,1,0,1,0,1,0,1,0,0,0,1,0,0,1,0,0,1,0,1}, {1,0,0,1,0,1,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0}, {0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0}, {1,0,1,0,1,0,0,1,0,0,0,1,0,0,0,1,0,1,1,0,0}, {0,0,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0}, {0,1,0,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1}, {1,1,0,1,0,1,0,0,0,1,0,0,0,1,0,0,1,0,0,1,0}, {0,0,1,1,0,1,0,0,0,0,1,0,0,1,0,0,1,0,0,0,1}, {1,0,1,0,1,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1}, {1,0,0,1,0,0,0,1,0,0,1,0,1,0,0,0,1,0,1,0,0}, {1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}}; int resultarray[14][21] = {{ 0 }}; for(row = 0, j = 0; row < 20; row++) { goodrow = 0; for(col = 0; col < 21; col++) { if(array[row][col] == 1) { goodrow = 1; //mark this row to be saved break; } } if(goodrow == 1) { for (col=0;col<21;col++) { resultarray[j][col] = array[row][col]; } j++; } } for(row=0;row<j;row++) { for(col=0;col<21;col++) { printf("%d",resultarray[row][col]); } printf("\n"); } return 0; }

Quote:

Originally Posted by Adak

You students nowadays, you expect code I post to be close to actually working! :)

Code:

#include <stdio.h> int main(int argc,char *argv[]) { int row, col, j; int goodrow=0; int array[20][21]={{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,1,0,1,1,1,1,0,0,1,0,1,0,1,0,1,0}, {0,0,1,0,1,0,1,0,1,0,0,0,1,0,0,1,0,0,1,0,1}, {1,0,0,1,0,1,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0}, {0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0}, {1,0,1,0,1,0,0,1,0,0,0,1,0,0,0,1,0,1,1,0,0}, {0,0,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0}, {0,1,0,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1}, {1,1,0,1,0,1,0,0,0,1,0,0,0,1,0,0,1,0,0,1,0}, {0,0,1,1,0,1,0,0,0,0,1,0,0,1,0,0,1,0,0,0,1}, {1,0,1,0,1,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1}, {1,0,0,1,0,0,0,1,0,0,1,0,1,0,0,0,1,0,1,0,0}, {1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}}; int resultarray[14][21] = {{ 0 }}; for(row = 0, j = 0; row < 20; row++) { goodrow = 0; for(col = 0; col < 21; col++) { if(array[row][col] == 1) { goodrow = 1; //mark this row to be saved break; } } if(goodrow == 1) { for (col=0;col<21;col++) { resultarray[j][col] = array[row][col]; } j++; } } for(row=0;row<j;row++) { for(col=0;col<21;col++) { printf("%d",resultarray[row][col]); } printf("\n"); } return 0; }

thanks boss

Hi: how to Traverse

Quote:

Originally Posted by mike_g

By traversing the array he basically means going through each element reading the content.

You could then have four variables: x_start, x_end, y_start, and y_end. When reading the array you would want to find these four points.

When you are finished reading you could then crop the array to everything between these co-ordinates.

How would i go on about traversing the the 2d array..
Thanks in Advance

You are already traversing the array.

Hi

Quote:

Originally Posted by Elysia

You are already traversing the array.

Hi there oh ok
but there is only one problem, my code is too genearlised.
the width and height of the array will change according to the file i open. so any idea, on how i can manipulate the width and height given that the maximum width is 50 and max height is 80

You know how much data you're reading, aren't you? Then you know the width and height of your array.

Quote:

Originally Posted by Elysia

You know how much data you're reading, aren't you? Then you know the width and height of your array.

Actuauly no i don't know. Because the width and height keeps changing.
my program will find find the width and height of the file. Bu the problem is i don't know how to specify the size of the resultant array.
mabye i could do it this ay, but any ideas ?
You could then have four variables: x_start, x_end, y_start, and y_end. When reading the array you would want to find these four points.

When you are finished reading you could then crop the array to everything between these co-ordinates.

Take it this way: you do read data into the array, so somehow you must know the size of the array and/or data, because otherwise you wouldn't be able to read it into the array, would you?
Therefore we must logically assume that you know x_start, x_end, y_start, y_end of the array (and btw, x_start and y_start should be 0).
Then you could basically read the array, find the data you want to keep and count that. From that information, you could create a new array and copy data over.
It's not unlike any normal life situation, you just have to think over it logically. You can create a flow chart - a chart that describes how you want the process to be done, in terms of words.
That's the first step of the process. After that, you translate it into code. But let's get the first part done first.

Can you post a small example of how your data changes, requiring the array to change. Just something small, but something to help clarify your description.

I don't have a clear enough picture yet, in my mind.

Quote:

Originally Posted by Adak

Can you post a small example of how your data changes, requiring the array to change. Just something small, but something to help clarify your description.

I don't have a clear enough picture yet, in my mind.

hi there
well all the files will have a variable width of 0 to 50, and a variable height of 0 to 80. But my program can find the height and width of the file. But the problem lies when i want to start to crop that array into a new array. i don't know the width and height of the new array as i can't open the file. the program will have to somehow find the row find the row that doen't contain all 0's in its column.
hope that is enough information.
thanks in advance

Quote:

Originally Posted by thamiz

i don't know the width and height of the new array as i can't open the file. the program will have to somehow find the row find the row that doen't contain all 0's in its column.

But this is what we're telling you is so easy.
If you traverse and read the array, you can determine how much data you need to copy.
You have already demonstrated that you know how to traverse an array.
The next step is to make sure the program remembers how much data it needs to copy.
Then you can create a new array and copy the data over.

Quote:

Originally Posted by Elysia

But this is what we're telling you is so easy.
If you traverse and read the array, you can determine how much data you need to copy.
You have already demonstrated that you know how to traverse an array.
The next step is to make sure the program remembers how much data it needs to copy.
Then you can create a new array and copy the data over.

Would a counter be advisable

Yes, a counter to count how many rows to copy might be advisable.

thanks again for your patience and time

Quote:

Originally Posted by Elysia

Yes, a counter to count how many rows to copy might be advisable.

i have a question
say if int a counter called goodrowcounter;
when i int the array[goodrowcounter][width];
my compiler say error: variable-sized objects may not be initialiased.
what can i do to rectify this problem

Quote:

Originally Posted by thamiz

i have a question
say i int a counter called goodrowcounter;
when i int the array[goodrowcounter][width];
my compiler say error: variable-sized objects may not be initialiased.
what can i do to rectify this problem

You need to use malloc to create a dynamic array (don't forget to free it using free later either).

Quote:

Originally Posted by Elysia

You need to use malloc to create a dynamic array (don't forget to free it using free later either).

how do i use malloc

Do you have a C book to learn from?