Write a function that takes an integer value and returns the number with its digits reversed. For example, given the number 7631, the function should return 1367.
I have no idea how to even start after i put the basic stuff in like the #include and int main. Somebody want to show me how they would do it and based off your program I'll do a similiar one.
read about integer operators / and % and think what will give you
number /10 and number %10
All problems in computer science can be solved by another level of indirection,
except for the problem of too many layers of indirection.
– David J. Wheeler
Say your integer was 21. The modulus operator is very nice for this, because it throws out the normal divide by 10 (which is what you want since we're base 10), answer, and shows you the remainder that is left over. 21 mod 10 == 1.Originally Posted by jturner38
Now we need to make the number 1 into the char '1'. The C library's itoa() is one way to do that.
So the one's column digit (1) has been handled. The 21 is still there, but we don't want to handle the 1 again, so we get rid of it, by dividing by 10. Now the number 2 is left in the one's column. Again, itoa() can be used on it, and the result added to the char we took out before (the one).
If you did this in a loop, it would be easy to put each digit into a char array[], and then print the array in the order you want.
This is a simple while or for loop block of code. You'll find the result very satisfying.
The problem can be solved by arithmetic means only:
Of course, this will need slight adjustments for negative values. If you stick with Adak's approach, here's a tip for choosing the right array size in advance: ceil(log(x, b)) will compute the number of digits needed to represent x in base b.Code:int rev(int x) { int ret = 0; while(x) { ret *= 10; ret += x % 10; x /= 10; } return ret; }
Greets,
Philip
PS: this solution is not intended to be used for copy'n'paste. On the other hand, you don't need to invent the trick with % and / yourself. From my experience, understanding it one time makes you able to remember it forever.
Last edited by Snafuist; 03-05-2009 at 04:15 AM.
All things begin as source code.
Source code begins with an empty file.
-- Tao Te Chip
You could also convert it to a string and then reverse the string, but that would probably be too wasteful.
"I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008
"the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010
Yes, seeing as converting it to a string involves the same number of essentially the same math operations, it seems a bit "going round the block to get next door".
--
Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
a complete answer
Code:int main() // starting of main funtion { int number, reverse=0, temporarydata; clrscr(); //to clear the screen printf("enter the number"); //printing and scanning scanf("%d", &number); while(number!=0) { temporarydata= number%10; // for last digit reverse= reverse*10 + temporarydata //allgori. for storring reverse //trie it yourself number=number \10; decreement by 10 } printf("The reverse number is : %d", reverse); getch(); return 0; }
