Help with C.

[protato117]

So I'm insanely new and fresh to coding with little to no experience at all.
 
can someone help me with C?

 

here's the code so far:

#include<stdio.h>#include<conio.h>main()	{	 int x,arr[7][9]={1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63};	 clrscr();	 for(x=0;x<63;x++);	  {	   printf("\t%d \t%d \t%d \t%d \t%d \t%d \t%d\n",arr[0][0],arr[0][1],arr[0][2],arr[0][3],arr[0][4],arr[0][5],arr[0][6]);	   printf("\t%d \t%d \t%d \t%d \t%d \t%d \t%d\n",arr[0][13],arr[0][12],arr[0][11],arr[0][10],arr[0][9],arr[0][8],arr[0][7]);	   printf("\t%d \t%d \t%d \t%d \t%d \t%d \t%d\n",arr[0][14],arr[0][15],arr[0][16],arr[0][17],arr[0][18],arr[0][19],arr[0][20]);	   printf("\t%d \t%d \t%d \t%d \t%d \t%d \t%d\n",arr[0][27],arr[0][26],arr[0][25],arr[0][24],arr[0][23],arr[0][22],arr[0][21]);	   printf("\t%d \t%d \t%d \t%d \t%d \t%d \t%d\n",arr[0][28],arr[0][29],arr[0][30],arr[0][31],arr[0][32],arr[0][33],arr[0][34]);	   printf("\t%d \t%d \t%d \t%d \t%d \t%d \t%d\n",arr[0][41],arr[0][40],arr[0][39],arr[0][38],arr[0][37],arr[0][36],arr[0][35]);	   printf("\t%d \t%d \t%d \t%d \t%d \t%d \t%d\n",arr[0][42],arr[0][43],arr[0][44],arr[0][45],arr[0][46],arr[0][47],arr[0][48]);	   printf("\t%d \t%d \t%d \t%d \t%d \t%d \t%d\n",arr[0][55],arr[0][54],arr[0][53],arr[0][52],arr[0][51],arr[0][50],arr[0][49]);	   printf("\t%d \t%d \t%d \t%d \t%d \t%d \t%d\n",arr[0][56],arr[0][57],arr[0][58],arr[0][59],arr[0][60],arr[0][61],arr[0][62]);	  }	 getch();	 return 0;	}

Output:

 

I do not completely understand how this code works or fully understand arrays at this point. I get the general idea of arrays, but I just don't know how to properly and effectively code it yet. 

 

and I'm also wondering how to get the same output using some for loop statements. and less lines of code. 

 

 

any help would be greatly appreciated! Thanks! 

 

p.s. links and other stuff that'll teach me about C would be appreciated as well! 

[Guest]

instead of that for should be

int i, j;int n = 7;int m = 9;int k = 0;for (i < 0; i < n; i++){       if (k == 0)         for (j = 0; j < m; j++)         {              printf(" %i", arr[i][j];              k = 1;         }       else         for (j = m-1; j > 0; j--)         {              printf(" %i", arr[i][j];              k = 0;         }       printf("/n");}

and when giving values to matrix you should add new line between each row.

 

and for tutorials go to https://buckysroom.org/index.php

[DavidTheWin]

I know this doesn't answer the question you asked, but if you're this new to programming then you definitely don't want to start with C. Start with a high level language like Java/C# which will introduce you to the concepts and design patterns for programming then move onto a lower level language like C to get a better feel for the implementation of languages e.g. pointers and memory management.

[Sauron]

instead of that for should be

int i, j;int n = 7;int m = 9;for (i < 0; i < n; i++){       for (j = 0; j < m; j++)       {             printf(" %i", arr[i][j];       }       printf("/n");}

and when giving values to matrix you should add new line between each row.

 

and for tutorials go to https://buckysroom.org/index.php

 

Maybe there's something I'm missing (or I'm just stupid ^^), but doesn't that print them in sequential order left to right? In the op the output was with the first line left to right, the second rigth to left, the third left to right again etc.

 

I think there should be an 'if' statement that checks if the value of i is even or odd (and print the values accordingly).

 

but again I'm tired and what I just wrote might make no sense...

[Guest]

Maybe there's something I'm missing (or I'm just stupid ^^), but doesn't that print them in sequential order left to right? In the op the output was with the first line left to right, the second rigth to left, the third left to right again etc.

 

I think there should be an 'if' statement that checks if the value of i is even or odd (and print the values accordingly).

 

but again I'm tired and what I just wrote might make no sense...

lol just noticed that.

I will edit it

[Sauron]

lol just noticed that.

I will edit it

 

Feels good to know I'm not completely crazy

[Guest]

Feels good to know I'm not completely crazy

look now, what you think

[Toltar]

Use a recursive function to make it efficient. All good algorithms have the ability to be implemented recursively.

[Sauron]

look now, what you think

 

looks perfect

[Guest]

Use a recursive function to make it efficient. All good algorithms have the ability to be implemented recursively.

I have feeling that OP is not that good at programming to use recursions.

[Toltar]

I have feeling that OP is not that good at programming to use recursions.

 

That could be true but its just a suggestion. 

[protato117]

I have feeling that OP is not that good at programming to use recursions.

not good enough yet at least

[protato117]

instead of that for should be

int i, j;int n = 7;int m = 9;int k = 0;for (i < 0; i < n; i++){       if (k == 0)         for (j = 0; j < m; j++)         {              printf(" %i", arr[i][j];              k = 1;         }       else         for (j = m-1; j > 0; j--)         {              printf(" %i", arr[i][j];              k = 0;         }       printf("/n");}

and when giving values to matrix you should add new line between each row.

and for tutorials go to https://buckysroom.org/index.php

I'll try this one!! thanks!!

[DavidTheWin]

Use a recursive function to make it efficient. All good algorithms have the ability to be implemented recursively.

 

Recursive algorithms are not always the most efficient method and just because something can be implemented using recursion does not always mean it should be.

[Toltar]

Recursive algorithms are not always the most efficient method and just because something can be implemented using recursion does not always mean it should be.

 

Based on the scenario of the OP and Big-Oh notation, having two for-loops causes a O(n^2) worst case scenario while having a recursive algorithm would make it more linear where the algorithm would be O(n). So O(n) would be better than O(n^2). But yes, in some cases it is the other way around as you have stated.

[DavidTheWin]

Based on the scenario of the OP and Big-Oh notation, having two for-loops causes a O(n^2) worst case scenario while having a recursive algorithm would make it more linear where the algorithm would be O(n). So O(n) would be better than O(n^2). But yes, in some cases it is the other way around as you have stated.

 

Nested for-loops is a form of recursion called tail recursion. I'd like to see your O(n) recursive algorithm for this because I'm not sure one exists.

[Avratz]

intmain(void){    int arr[63] =   {                        1,2,3,4,5,6,7,                        8,9,10,11,12,13,14,                        15,16,17,18,19,20,21,                        22,23,24,25,26,27,28,                        29,30,31,32,33,34,35,                        36,37,38,39,40,41,42,                        43,44,45,46,47,48,49,                        50,51,52,53,54,55,56,                        57,58,59,60,61,62,63                    } ;    int x = 0;    for(; x < 63; x++)        printf((x+1)%7?"\t%d":"\t%d\n",(arr+x/7*7)[x/7&1?6-x%7:x%7]);    return 0;}

I'd buy a book. http://www.amazon.com/Programming-3rd-Stephen-G-Kochan/dp/0672326663/ref=sr_1_8?s=books&ie=UTF8&qid=1415929027&sr=1-8&keywords=c+programming

[madknight3]

Speaking of books The C Programming Language by Kernighan & Ritchie is a great book I would highly recommend.

[smjpl]

snip

 

 

snip

 

Here are some free ones. There are books for loads of languages so I just quoted the ones for C.

 

GitHub – 500 free programming books

 

C

• A Tutorial on Pointers and Arrays in C
• Beej’s Guide to C Programming
• Beej’s Guide to Network Programming
• The C book
• Essential C (PDF)
• Learn C the hard way
• The new C standard – an annotated reference
• Object Oriented Programming in C (PDF)
• C Programming – Wikibooks

[Midnight]

Use a recursive function to make it efficient. All good algorithms have the ability to be implemented recursively.

 

That's overkill here.

[protato117]

thank you guys so much I'll be sure to check all of these out!!

[Art Vandelay]

I know this doesn't answer the question you asked, but if you're this new to programming then you definitely don't want to start with C. Start with a high level language like Java/C# which will introduce you to the concepts and design patterns for programming then move onto a lower level language like C to get a better feel for the implementation of languages e.g. pointers and memory management.

I'll never understand why people keep saying this. When you're starting, it's all the same. You're not going to be calling malloc or needing to create a complex structure, you're just going to go do some basic things with compiler managed primitive variables. The only downside to C in that respect is that windows will terminate the program when you try to access an array out of its bounds, instead of it telling you that you tried to do that, but once you know that that's the reason it's pretty much the same to debug.

Java/C# introduces a whole extra level of complexity with classes and API calls. I never found classes easy to understand when I started and the API calls in Java/C# still confuse me sometimes, years later.

 

 

Use a recursive function to make it efficient. All good algorithms have the ability to be implemented recursively.

What? How would recursion make it faster? Recursion is almost always slower and more uses more memory, in C, than iteration.

 

Generally recursion is used in C because making some algorithms iteratively is horrific to do. Navigating a non binary tree iteratively hurts.

[protato117]

intmain(void){    int arr[63] =   {                        1,2,3,4,5,6,7,                        8,9,10,11,12,13,14,                        15,16,17,18,19,20,21,                        22,23,24,25,26,27,28,                        29,30,31,32,33,34,35,                        36,37,38,39,40,41,42,                        43,44,45,46,47,48,49,                        50,51,52,53,54,55,56,                        57,58,59,60,61,62,63                    } ;    int x = 0;    for(; x < 63; x++)        printf((x+1)%7?"\t%d":"\t%d\n",(arr+x/7*7)[x/7&1?6-x%7:x%7]);    return 0;}

I'd buy a book. http://www.amazon.com/Programming-3rd-Stephen-G-Kochan/dp/0672326663/ref=sr_1_8?s=books&ie=UTF8&qid=1415929027&sr=1-8&keywords=c+programming

 

I'm tryna make sense out of this code but I can't seem to fully understand it...can you please explain this further? just the printf bit at least... 

[madknight3]

I'm tryna make sense out of this code but I can't seem to fully understand it...can you please explain this further? just the printf bit at least... 

Unless you're doing something like code golf, don't write code like that. Write nice code that is, at least, reasonably easy to read and understand lol

[Art Vandelay]

I'm tryna make sense out of this code but I can't seem to fully understand it...can you please explain this further? just the printf bit at least... 

I think it works out to:

		// % is the modulo operator		if ((x+1)%7 != 0) //(x+1)%7?"\t%d":"\t%d\n" this is a ternary operator, basically if-else on the same line. 0 means false, not 0 means true in a boolean expression, you don't need a comparison.		{			if ((x/7) % 2 == 1) //x/7&1?6-x%7:x%7 another ternary operator. & is the logical AND operation. doing &1 checks the last binary digit, which is 1 if odd, 0 if even.			{				printf("\t%d",(arr)[x/7*7 + 6-x%7]); //x/7 is the row at which the point is. Adding to the variable arr is the same as adding the same number to the index								     //this is because arr is the memory index of the first element of the array, and adding 1 to arr iterates                                                                      //the memory index by 1, pointing to the next index		                                                     //note that iterating the memory pointer by 1 moves you 1*(the size of the data type) in memory			}			else 			{				printf("\t%d",(arr)[x/7*7 + x%7]);			}		}		else		{			if ((x/7) % 2 == 1)			{				printf("\t%d\n",(arr)[x/7*7 + 6-x%7]);			}			else 			{				printf("\t%d\n",(arr)[x/7*7 + x%7]);			}		}	}

Hopefully that helps, and please never use modulo ternary operators in your code. They are very irritating to read. 

 

edit: I said modulo instead of ternary by accident. I don't really proof read.