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any one know who to make loop on this??
how to loop over and over again till i prest "-1" then only the program end
Code:#include<stdio.h>
#include<string.h>
void main()
{
char strsrc[5];
char strtmp[5];
printf("\n Enter a five-digit number ( -1 to end ): "); gets(strsrc);
strcpy(strtmp,strsrc);
strrev(strtmp);
if(strcmp(strsrc,strtmp)==0)
printf("\n %s is a palindrome\n",strsrc);
else
printf("\n %s is not a palindrome\n",strsrc);
}
Use while ...
--
Mats
FAQ Entry: How do I get a number from the user (C)
FAQ Entry: Get a line of text from the user/keyboard (C)
Tutorial: Loops in C
where do i need to put the while?
Mats you mean <math.h>
?
Not forgetting the FAQ on void main as well.
this not working cuz its says !=' : no conversion from 'const int' to 'char *'Code:#include<stdio.h>
#include<string.h>
void main()
{
char strsrc[5];
char strtmp[5];
printf("\n Enter a five-digit number ( -1 to end ): "); gets(strsrc);
strcpy(strtmp,strsrc);
strrev(strtmp);
while (strsrc!=-1)
if(strcmp(strsrc,strtmp)==0)
printf("\n %s is a palindrome\n",strsrc);
else
printf("\n %s is not a palindrome\n",strsrc);
}
That's because you don't compare strings with !=. You compare strings with strcmp.
Also, you would need to compare with the string "-1", not the number -1.
then its must be like this?
this still erroe thou...Code:#include<stdio.h>
#include<string.h>
void main()
{
char strsrc[5];
char strtmp[5];
printf("\n Enter a five-digit number ( -1 to end ): "); gets(strsrc);
strcpy(strtmp,strsrc);
strrev(strtmp);
while (strcmp!="-1")
if(strcmp(strsrc,strtmp)==0)
printf("\n %s is a palindrome\n",strsrc);
else
printf("\n %s is not a palindrome\n",strsrc);
}
So if "you" did this one right:
why do you think it should beCode:if(strcmp(strsrc,strtmp)==0)
?Code:while (strcmp!="-1")
because matsp says use while, and i dono where to used the while...
Who's complaining about the while? It's the only thing right about that second quoted line.
i still dont get you sir.. do you mind correct that code please..
You cannot use operators like !=, == with strings. Besides, strcmp is not even a string, it is a pointer to an array of char.Code:while (strcmp(strcmp, "-1") !=0) {
...
}
Why test with -1 for a string by the way?? I don't know if this will work. If you enter -1 that will be two characters saved inside strsrc. If you reverse them, with strrev(), I assume you will have 1- as a string, not -1. You can just press "quit" or 'q' to quit the program...
StormRoBoT, try doing these tasks first:
- Write a program that reads in a word of no more than 5 letters and prints the word in reverse.
- Write a program that reads in a word and of no more than 5 letters and prints "Correct!" if the word is "Storm" and "Wrong!" otherwise.
- Write a program that reads in words of no more than 5 letters. While the word is not "-1", print the word and read another word, otherwise end the program.
Once you are done with these three tasks, you will have a better idea of how to combine them to solve your current problem.
its not working,
any way you got any idea on how to do this in other way? where if i keyin -1 it will terminate the program..
something like this
Code:Enter a five-digit number ( -1 to end ): 21212
21212is a palindrome
Enter a five-digit number ( -1 to end ): 16633
16633 is not a palindrome
Enter a five-digit number ( -1 to end ): -1
Show your current code.Quote:
its not working
Yes, but you should try and come up with it yourself. As I suggested, if you are having trouble solving your entire problem at one go, break it down into parts and solve each part separately, then combine the knowledge you gain from solving them separately to help you solve the entire problem.Quote:
any way you got any idea on how to do this in other way? where if i keyin -1 it will terminate the program..
my current codeCode:#include<stdio.h>
#include<string.h>
void main()
{
char strsrc[5];
char strtmp[5];
printf("\n Enter a five-digit number ( -1 to end ): "); gets(strsrc);
strcpy(strtmp,strsrc);
strrev(strtmp);
while (strcmp(strcmp, "-1") !=0) {
if(strcmp(strsrc,strtmp)==0)
printf("\n %s is a palindrome\n",strsrc);
else
printf("\n %s is not a palindrome\n",strsrc);
}
}
You should indent it properly, e.g.,
Now, where is strrev() defined? As far as I can tell, you are trying to use a function that does not exist. Even before implementing your while loop, this should have come to your attention.Code:#include<stdio.h>
#include<string.h>
int main()
{
char strsrc[5];
char strtmp[5];
printf("\n Enter a five-digit number ( -1 to end ): ");
gets(strsrc);
strcpy(strtmp,strsrc);
strrev(strtmp);
while (strcmp(strcmp, "-1") !=0) {
if(strcmp(strsrc,strtmp)==0)
printf("\n %s is a palindrome\n",strsrc);
else
printf("\n %s is not a palindrome\n",strsrc);
}
return 0;
}
Stop what you are doing right now and complete the tasks that I outlined. You are clearly jumping into the problem without making effort to break it down into parts and confirm that the individual pieces are working before integrating them. At this rate, you have no hope of finishing this simple problem since any attempt to fix the loop will not fix the problem as you are not even reversing the string, and any attempt to fix the string reversal will not fix the problem since the loop is incorrect.
Oh, and you really should not be using gets(). Use say, fgets() instead (and you will discover that you actually want strsrc and strtmp to have 6 chars, not 5).
EDIT:
Actually, since you already have some idea of how to use strcmp(), you could actually accelerate working through the smaller tasks:
- Write a program that reads in a word of no more than 5 letters and prints the word in reverse.
- Write a program that reads in a word of no more than 5 letters and prints "Yes!" if the word is a palindrome, otherwise print "No!".
- Write a program that reads in words of no more than 5 letters. While the word is not "-1", print the word and read another word, otherwise end the program.
So your final program would basically be: write a program that reads in words of no more than 5 letters. While the word is not "-1", (print "Yes!" if the word is a palindrome, otherwise print "No!") and read another word, otherwise end the program.
Nonetheless, resist the urge to jump tasks.
oh ok wait actualy my code is this
Code:#include<stdio.h>
#include<string.h>
void main()
{
char strsrc[5];
char strtmp[5];
printf("\n Enter a five-digit number ( -1 to end ): "); gets(strsrc);
strcpy(strtmp,strsrc);
strrev(strtmp);
if(strcmp(strsrc,strtmp)==0)
printf("\n %s is a palindrome\n",strsrc);
else
printf("\n %s is not a palindrome\n",strsrc);
}
strrev <<< this mean revers the caracter so that i can compare with the origenal one witch is user have keyin
Be warned that strrev() is not in the standard C library.Quote:
strrev <<< this mean revers the caracter so that i can compare with the origenal one witch is user have keyin
then what are other method that i can use?
and i need it to repeat over and over again..
Implement it yourself. Actually, you do not need to reverse the entire string to determine if it is a palindrome... but perhaps you can change this later.Quote:
then what are other method that i can use?
When you say it doesn't work what do you mean?
Does it work when you not check for the -1? Just when you check if it is a palindrome?
And you where noted that you will need 6 char for the strings. Five for the digits, one for the null character. Change it. Then if strrev() works correctly the program should work (I suppose).
Now, if you want to add the -1 thing to terminate then I already suggested why it wouldn't work. Again, -1 is two characters. If you reverse this string "-1", you get this string "1-". Don't mix characters with numbers. So you can check for "1-" to terminate. But if this is not actually a requirement, as I already said, it is not very "nice" to do so. Better check for "quit" or another key word/character. The idea of -1 is good if you actually read int from the input not characters.
what i wan is when i run the program the program execute it over and over again...
this code that i have post here is only can test for 1 time then the program end, but i wan its over and over again till i key in -1 then only the program end
some thing like this
do you get me?Code:Enter a five-digit number ( -1 to end ): 21212
21212is a palindrome
Enter a five-digit number ( -1 to end ): 16633
16633 is not a palindrome
Enter a five-digit number ( -1 to end ): -1
can i do this in division and remainder operators to separate the number into its individual digits?
Anyway, we are making circles here. Here is what you want (even though I already posted it)
Try this and it will end properly.
But AGAIN, you have MORE errors. So do this:
the above will print OK until you press -1. You NEED to clean the remaining characters. If you don't, then if somebody enters 5 digits the \n will remain (since they pressed enter). So next time that will be read. To avoid this, you call one more fgets() which will read everything that is left and "clean" stdin. If somebody enters more than 5 digits, then the first five will be read and the remaining will be cleaned. In any way this should work for you for (almost, don't try to prove me wrong) all input.Code:#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char strsrc[6];
char clean[100];
while(1) {
printf("Enter 5 digits or -1 to exit: ");
fgets(strsrc, 6, stdin);
if (strcmp(strsrc, "-1\n") ==0) break; //exit while
printf("OK\n"); //otherwise print OK
fgets(clean, 100, stdin); //clean remaining characters
}
}
EDIT: fgets reads also the \n, so if you enter -1 you will actually have "-1\n". So I changed the strcmp to include this
fgets(strsrc, 6, stdin);
I prefer
fgets(strsrc, sizeof strsrc, stdin);
so no question arises what is magic 6
and also no problem could appear if the size of the array is suddenly changed
if the string was read fully - this call will require user to press enter once again - better to check that the \n is not present in the strsrc buffer before calling this "cleaning" fgetsQuote:
//clean remaining characters
At what point does your program exit?
Yup, sizeof() is much better, it was a mistake not to have it.Quote:
Originally Posted by vart
As for the freezing, it will also freeze if you only enter 2 or 3 digits. It was just a sample code, not meant to be perfect, that is the OP's job. I just added it because otherwise it will be completely wrong since it would automatically read again...
There was a recent post about palindromes. There, the guy (or gal) used the / and % to seperate the digits. In other words he had an array of int to work with. There we proposed again a working solution, but you will see (if you search with palindrome as a key word) that it is much more difficult. Stringwise is much better.Quote:
Originally Posted by StormRoBoT
If strrev() is the problem and doesn't work, write it your own or google it and copy it. Stick with what you have
Code:/*
** STRREV.C - reverse a string in place
**
** public domain by Bob Stout
*/
#include <string.h>
char *strrev(char *str)
{
char *p1, *p2;
if (! str || ! *str)
return str;
for (p1 = str, p2 = str + strlen(str) - 1; p2 > p1; ++p1, --p2)
{
*p1 ^= *p2;
*p2 ^= *p1;
*p1 ^= *p2;
}
return str;
}
Using xor to swap the elements is really not so clever these days, as it makes the dependance chain longer in the processor. In the old days, when processors were slow and memory was (relatively speaking) fast, saving a register may have made a difference. In a modern processor, I'm 99.9% sure that a regular "temp = a; a = b; b = temp" type swap is a better choice. [Of course, it probably takes a string that is several hundred K to make any noticable difference, but that is sort of another problem].
--
Mats
Are you calling me unclever? Besides, Bob Stout (whoever that is) wrote this code, not me. I just copied and pasted the first google result. With all the profiling and crap the compiler does these days you are probably right. Next time I will copy and paste the second google result ;)
Some empirical evidence:
The result is:Code:#include <stdio.h>
#include <string.h>
#include <time.h>
char *astrrev(char *str)
{
size_t len;
size_t i;
if (! str || ! *str)
return str;
len = strlen(str)-1;
for (i = 0; i < len / 2; i++)
{
char t = str[i];
str[i] = str[len-i];
str[len-i] = t;
}
return str;
}
char *bstrrev(char *str)
{
char *p1, *p2;
if (! str || ! *str)
return str;
for (p1 = str, p2 = str + strlen(str) - 1; p2 > p1; ++p1, --p2)
{
*p1 ^= *p2;
*p2 ^= *p1;
*p1 ^= *p2;
}
return str;
}
void testit(char *(*func)(char *), char *name)
{
char str[3][20] = { "abc", "aabbcc", "abcdefgh" };
int i, j;
clock_t t;
for(i = 0; i < 3; i++)
{
printf("strrev(%s)=", str[i]);
printf("%s\n", strrev(str[i]));
}
t = clock();
for(j = 0; j < 10000000; j++)
{
for(i = 0; i < 3; i++)
{
func(str[i]);
}
}
t = clock() - t;
printf("%s: %f\n", name, (double)t / CLOCKS_PER_SEC);
}
#define TESTIT(x) testit(x, #x)
int main()
{
TESTIT(astrrev);
TESTIT(bstrrev);
TESTIT(strrev);
return 0;
}
So the winner is MS, with my function about 20% faster than the XOR method. Under some circumstances, a 20% speed up is definitely a good thing!Code:strrev(abc)=cba
strrev(aabbcc)=ccbbaa
strrev(abcdefgh)=hgfedcba
astrrev: 0.828000
....
bstrrev: 1.078000
...
strrev: 0.781000
--
Mats
wah.. this realy complicated..
but i still cant fint the way to make it like this..
Code:Enter a five-digit number ( -1 to end ): 18181
18181 is a palindrome
Enter a five-digit number ( -1 to end ): 12345
12345 is not a palindrome
Enter a five-digit number ( -1 to end ): -1
> So the winner is MS, with my function about 20% faster than the XOR method. Under some circumstances, a 20% speed up is definitely a good thing!
Well that goes to show you that google results are not always in the order of "most optimal" or "fastest performance." I will google it again and give that Bob Stout guy a stern talking to. Its times like these that I am glad I always give due credit within comments so that any complaints can go to the author of the code... That and its unethical to claim another's work as your own. But in honestly, its mostly to fan the flames in the proper direction.
Hmmm this has some limitations... but what if you did this:
Example:
Code:static const int primes[] = {02,03,05,07,013,015,021,023,027}; // yep.. I used octals... I am bored
long unsigned long key_fstring(const char *s)
{
long unsigned long r = 0;
if(s)
for(r = 1;*s;++s)
r *= primes[*s - '0'];
return r;
}
long unsigned long key_rstring(const char *s)
{
long unsigned long r = 0;
const char *begin = s;
if(s)
for(r = 1, s += strlen(s) - 1;s >= begin;--s)
r *= primes[*s - '0'];
return r;
}
int main(void)
{
char buffer[256], *p, *end;
int x;
do
{
puts("Please input a number:");
fgets(buffer, sizeof(buffer), stdin);
strtok(buffer, "\n");
x = strtol(buffer, &end, 10);
if(end != buffer)
{
x = +x;
snprintf(buffer, sizeof(buffer), "%d", x);
/* All that has been done up to this point is the gathering of the user input, less user idiocy */
printf("%d is%sa palindrome.\n", x, (key_fstring(buffer) == key_rstring(buffer))?" "," not ");
}
} while(*buffer);
return 0;
}
I fail to see why. You where more or less provided with every necessary code you needed to finish and correct your code. You had like 90% of the code done yourself in the first place. Post what you don't understand from the code(s) providedQuote:
Originally Posted by StormRoBoT
EDIT: necessary code needed....sigh
this is some other code, but still i need help on looping, where should i put my while?Code:#include <stdio.h>
#include <iostream.h>
void main()
{
int a , b;
int n;
printf("Enter a five-digit number ( -1 to end ): \n");
scanf("%d",&n);
a = n;
b=0;
while(a>0)
{
b *= 10;
b += a%10;
a /= 10;
}
if(b == n)
{
printf("%d is a palindrome\n" , n);
}
else
{
printf("%d is not a palindrome\n" , n);
}
}
i need to put something likebut i dont know where to put itCode:while (n!=-1)
Have you made any effort to figure this looping out on your own? It's really not hard, if you actually think about it, and don't expect it to be spoon-fed to you. I have twice linked you to the lesson on loops here at cprogramming.com, and I suspect you haven't even looked at it.
Oh, here's an idea...EXPERIMENT!!!!Quote:
Originally Posted by StormRoBoT
Final post.
This means that the code inside the brackets ({, }) will be executed repeatedly while n is not equal to -1. Thus it will only stop when n is equal to -1.Code:while(n!= 1) {
//do something
}
So put inside the brackets the code you want to be executed repeatedly.
Over and out
i got the loop here
but its seems that my formular is wrong, cuz all the number i have enter its says not a palindromeCode:#include <stdio.h>
#include <iostream.h>
void main()
{
int a , b;
int n;
printf("Enter a five-digit number ( -1 to end ): \n");
scanf("%d",&n);
a = n;
b=0;
while(n!=-1)
{
b *= 10;
b += a%10;
a /= 10;
if(b == n)
{
printf("%d is a palindrome\n" , n);
printf("Enter a five-digit number ( -1 to end ): \n");
scanf("%d",&n);
}
else
{
printf("%d is not a palindrome\n" , n);
printf("Enter a five-digit number ( -1 to end ): \n");
scanf("%d",&n);
}
}
}
can any one help?
Because your while-loop is wrong. You need two loops, one to repeat the input of numbers and all the code to check if the number is a palindrome and another one that covers the three lines that reverses the number. Currently, you are copying the last digit of a (or n) into b, but the remaining digits are still in a. You need to continue moving digits from a to b until there are no digits left in a.
--
Mats
What with including <iostream.h>? That's from pre-standard C++, and this is C. You got it right earlier by including <stdio.h>.
Take a good look at the code below:
It is basically your current code, except that it is well indented, includes the correct header, uses int main() instead of void main(), corrects the loop condition (you forgot to assign n to a, but with such undescriptive variable names, it is hard to know what is a and b anyway), shifts the duplicated code out of the if and else blocks, and... uses a function to determine if the number is a palindrome. Now you need to implement that function.Code:#include <stdio.h>
int isPalindrome(int n);
int main()
{
int n;
printf("Enter a five-digit number ( -1 to end ): \n");
scanf("%d", &n);
while (n != -1)
{
if (isPalindrome(n))
{
printf("%d is a palindrome\n", n);
}
else
{
printf("%d is not a palindrome\n", n);
}
printf("Enter a five-digit number ( -1 to end ): \n");
scanf("%d", &n);
}
return 0;
}
/* Return 1 if n is a palindrome, else return 0. */
int isPalindrome(int n)
{
/* ... */
}
Right, so I have been pretty generous with the above, and I hope that at the very least in your future code you will indent your code properly and use descriptive names.
Psh... I don't see what the problem was to my approach. And since I used 64-bit numbers you can even have reasonably long numbers before buffer overflows come out to play.
i have finaly make this program work the way i wanth.. thanks guys...
this is the code that i have used..
:cool:Code:#include <stdio.h>
void main()
{
int a , b, c, d;
int n;
int temp;
printf("Enter a five-digit number ( -1 to end ): \n");
scanf("%d",&n);
while(n!=-1)
{
a =n /10000;
temp=n%10000;
b =temp /1000;
temp=n % 100;
c=temp/10;
temp=n%10;
d =temp/1;
if(a == d && b == c)
{
printf("%d is a palindrome\n" , n);
printf("Enter a five-digit number ( -1 to end ): \n");
scanf("%d",&n);
}
else
{
printf("%d is not a palindrome\n" , n);
printf("Enter a five-digit number ( -1 to end ): \n");
scanf("%d",&n);
}
}
}
It's going to be a long road. 20 posts, and you're still using void main, and you still can't indent code at all.
what?? dont get you.. i said i have made the program work the way i wan it..Quote:
Originally Posted by Salem
You mean the way your current compiler lets you get away with.
Sooner or later, you'll change compiler. Only then will you discover that the slap-happy "works for me" approach was a folly. Been there, done that. If you want the T-shirt as well, then that's up to you.
Your code is already at the limits of understandability without any indentation. If it were 10 times longer, people would just ignore you.
int main (void)Quote:
Originally Posted by StormRoBoT
{
int a, b, c, d;
int n;
int temp;
do
{
printf("Enter a five-digit number < -1 to end >: ");
scanf(" %d", &n); // if you are going to ask the user for input over and over again, it is always good to clear the input stream.
a = n / 10000;
temp = n % 10000;
b = temp / 1000;
temp = n % 100;
c = temp/10;
temp = n%10;
d = temp/1;
if(a == d && b == c)
printf("%d is a palindrome\n", n);
else
printf("%d is not a palindrome\n" , n);
while (n != -1); // as long as n is NOT -1, the loop continues.
return 0;
}
I believe this code would do a better job than yours, you don't have to use scanf and printf over and over again. Just use a do while loop and set your condition to check whether n is NOT -1.
Use code tags for posting codeQuote:
I believe this code would do a better job than yours, you don't have to use scanf and printf over and over again. Just use a do while loop and set your condition to check whether n is NOT -1.
1. What will happen to your code if user enters string instead of number?
2. What will happen to your code if user enters 6-digit number?
3. etc