So I have only ever programmed in c++, but I have to do a small homework that requires the use of c. The problem I encountered is where I need a loop to read in numbers separated by spaces from the user (like: 1 5 6 7 3 42 5) and then take those numbers and fill an array.
the code I wrote is this:
int i, input, array[10];
for(i = 0; i < 10; i++){
scanf("%d", &input);
array[i] = input;
}
EDIT: added array definition.
any suggestions or hints would be very highly appreciated.
Irrespective of whatever is wrong here, you should quickly learn to NEVER write code that does not check the return value from any API call that you make. scanf returns a value, and you have to be interested in what it says. If the call fails, your logic is different, yes?
Perhaps in this case it would tell you what's going wrong. The docs are here.
Returns the number of fields
successfully converted and assigned;
the return value does not include
fields that were read but not
assigned. A return value of 0
indicates that no fields were
assigned.
This code working good.
If your numbers is less than 10, then you must know how many numbers is before you start reading this numbers, or last number must be something like 0 to terminate output then you can do while(true) loop, but for dynamically solution you must read all line into string and then using sscanf to reading numbers from this string.
You need the right #include and a proper main. The following works for me
#include <stdio.h>
int main(void) {
/* YOUR CODE begin */
int i, input, array[10];
for (i = 0; i < 10; i++) {
scanf("%d", &input);
array[i] = input;
}
/* end of YOUR CODE */
return 0;
}
i'm not a c programmer but i can suggest an algorithm which is to use scanf("%s",&str) to read all the input into a char[] array then loop over it and test using an if statment if the current char is a space, if it is then add the preceeding number to the array
Related
Currently learning C - and I have no clue where I'm going wrong in this code:
#include <stdio.h>
int main()
{
char alphabet[20];
int i;
for (int i = 0; i > 20; i++)
{
printf("Enter in a letter:\n");
scanf("%s", alphabet[i]);
if (alphabet[i] == alphabet[i+1])
{
printf("Duplicate Letters");
};
return 0;
}
}
The program that I am asked to make for class — I'm required to create a 1D array, add validation for alphabetical letters and duplicate letters, as well as creating a function for sorting the letters and specifying the number of times each letter was put in.
As much as I've been able to attempt coding is:
Create a 1D array to read 20 alphabetical letters
Add validation for duplicate letters and printf 'Duplicate Letters'
but every time I try, the program terminates at 'Enter in a letter:' or it won't execute.
Where did I go wrong?
For background: I work mainly on Windows 7 because that's what the school has — using MinGW as my compiler — but for working at home I use MacOS using Terminal as the compiler.
for (int i = 0; i > 20; i++)
You're telling the computer here to initialize i to 0, and then, while i is greater than 20, do the loop. However, since i starts at 0, it will never be greater than 20.
for (int i = 0; i < 20; i++)
And, yes, as comments have pointed out, your use of scanf is incorrect. Lacking a better C reference for it, check out http://www.cplusplus.com/reference/cstdio/scanf/ for descriptions of its arguments.
So i have a few questions about reading into arrays(very new to c)
I have this code so far
int xZac[stCrt];
int xKonc[stCrt];
int yZac[stCrt];
int yKonc[stCrt];
for (int i=0; i < stCrt; i++) {
scanf("%d", &xZac[i]);
scanf("%d", &yZac[i]);
scanf("%d", &xKonc[i]);
scanf("%d", &yKonc[i]);
int c = xKonc[i]-xZac[i];
printf("%d", c);
//the values here shoud be xKonc[0]=49, xZac[0] = 0, it outprints 490
// but i need the actual difference between those in other inputs
//it also only returns it once even tho on the first input there should be 2 such values
//on another instance(maybe im reading them wrong?) xKonc[0]=29 and xZac[0]=0 but the output is 2907220
}
Is this the proper way of reading into an array?
How do i then get the value of this, i need to use it in for statement later on but i cant seem to get it right. How would i say get the number of xKonc[i]-xZac[i]. it seems to return pointers or something when i try it. So what id like to know is how to subtract actual integers from arrays, and if im reading the data right or is the problem there
I don't see anything obviously wrong with this. Can you include your input file? I would venture to bet you are printing a 49 and a 0, without a newline character, causing you to think you are printing 490
I'm working on a project at the moment where I have to allow a user to enter an infinite amount of numbers and reverse the order of those entered numbers and end the program if 0 is entered. I did something similar, except the one I did set the amount of numbers the user could enter, so for example in the code below, I allowed the user to enter only three numbers, reverse the order and end when -1 is entered.
#include <stdio.h>
#define MAX 3 // Defining max amount of numbers to be entered to 3
main()
{
int numbers[MAX], i, end;
printf ("Please enter %d integers:\n", MAX);
for (i = 0; i < MAX; i++){
scanf("%d", &numbers[i]);
if (numbers[i]==-1){ // Loop ends when -1 is entered
for (end=i; end<MAX; end++)
numbers[end]='\0'; // Nulls the value of blank locations in the array
i=MAX;
}
}
printf ("\nThe values in reverse order are:\n");
for (i = MAX-1; i >= 0; i--)
{
if(numbers[i]!='\0') // Will not print null values in the array
printf("\n%d ", numbers[i]);
}
return 0;
}
How can I go about achieving this? I'm guessing I won't be able to use an array, and I'm pretty new to this so...
No, arrays can't be grown dynamically (not without some extra tinkering, see comment below) so they can't hold an infinite amount of items.
You'll need some structure you can grow, C doesn't provide one so you'll have to use a third party implementation or write your own. A stack fits your problem the best.
Also, your loop will have to go on until -1 is entered. Either an infinite loop with a break statement, or a do-while loop that checks the entered number.
EDIT: The original question targeted C++, my original answer, below, is no longer relevant.
You want to look into C++'s STL. std::vector, std::deque or std::stack for example, would be useful in your case.
You can use a std::vector to do this.
Here's the declaration of your std::vector. Where the tells the vector you want it to be a vector of type int
std::vector<int> numbers;
Then to add to the end of the std::vector you use push_back(), which puts the integer onto the back of the array. The size of the vector will dynamically increase as you push more elements on to the back.
int input;
numbers.push_back(input);
Then to iterator through it you can use a reverse iterator or just iterate the same way you have been doing it using numbers.size() to find out how many elements are in the vector.
My teacher gave an assignment to me. The question is below:=
Write a program that prompts the user to enter 10 double numbers. The program should accomplish the follwing:
a. Store the information in a 10-element array.
b. Display the 10 numbers back to the user.
I could do all of the above in main().
Hint: You should use loops, not hardcode the values 0 through 9. It should be easy to convert your program to accept 1000 numbers instead of 10.
For a bonus mark, do at least one of the tasks (a or b) in a separate function. Pass the array to the function; do NOT use global (extern) variables.
I confused above. I wrote a program in the source code. Am I doing wrong? It is below:=
#include<stdio.h>
int main(void)
{
int number[10];
int i;
for (i = 0; i <10; i++)
printf("%d.\n", i, number[i]);
printf("\n\nPress [Enter] to exit program.\n");
fflush(stdin);
getchar();
return 0;
}
Thanks.
Not too bad so far, I'd like to make the following comments:
if you need to input double numbers, you should probably use double rather than int.
you need a statement (maybe in your current loop but possibly in another loop preceding the current one) which inputs the numbers. Look into scanf for this.
Using %d with printf is for integers, not doubles. You will have hopefully already figured out the format string to used when you looked into scanf above.
Bravo for using the correct int main(void) form and for not including conio.h :-)
Once you've figured those bits out, then you can worry about doing it in a separate function.
Based on the code you have given above, I would suggest reading up on the following:
scanf
functions in C, particularly passing arrays to functions: this link should be good.
Note to OP: If you were able to do (a) and (b) in main(), the code above is not complete. It would be nice the functions you created for getting (a) and (b) above done for getting to the root of your "confusion".
Let me know in case you need more help.
HTH,
Sriram
Try this it may sloves your problem.
#include<stdio.h>
int main(void)
{
double number[10];
int i;
printf("Enter double numbers:");
for (i = 0; i <10; i++)
scanf("%lf",&number[i] );
printf("The numbers you entered are:");
for (i = 0; i <10; i++)
printf("%lf\n",number[i] );
return 0;
}
What I want to do is reverse a string of numbers that the user enters. what happens is it compiles and runs till i hit enter after the scanf. then I get some Microsoft runtime error... what's going wrong???
NOTE: this is homework, but i've got the logic figured out. what baffles me is this error.
#include <stdio.h>
int main()
{
unsigned int giveStr = 0;
char* charIt;
printf("Enter a number to be reversed.\t");
scanf("%d", &giveStr);
fflush(stdin);
sprintf(charIt, "%d", giveStr);
revStr(giveStr);
getchar();
return 0;
}
revStr(unsigned int n)
{
char buffer[100];
int uselessvar, counter = 0;
for (; n > 0;)
{
uselessvar = sprintf(&buffer[counter], "%d", n);
counter++;
}
for (counter = 0; counter > 0;)
{
printf("%c", buffer[counter]);
counter--;
}
return 0;
}
EDIT: flushing stdin for newlines :/ and also image here just not with that program. with mine.
You are trying to access memory which is not allocated in:
sprintf(charIt, "%d", giveStr);
Change char* charIt; to char charIt[50]; and all should be well (well, at least the segmentation fault part)
Also... pass charIt to revStr, as charIt contains the string with our number.
Then, a simple for loop in revStr will do the trick (what was the purpose of the second one, anyway?)
void revStr(char *giveStr)
{
int counter;
for (counter = strlen(giveStr)-1; counter >= 0; counter--)
{
printf("%c", giveStr[counter]);
}
printf("\n");
}
This will print each char our char representation has from the last one till the first one. You should read more on for loops.
For your home work problem, if you have the K&R book, turn to section 3.5 and read it thoroughly.
Note the functions reverse() and itoa(). They should give you a pretty good idea on how to solve your problem.
How does your program get out of the for (; n > 0;) loop? Won't counter simply increase until you get a bus error?
ED:
Respectfully, I think the claim that "i've got the logic figured out" is a little optimistic. :^) Doubtless someone will post the way it should have been done
by the time I'm done writing this, but it's probably worth drawing attention to what went wrong (aside from the memory allocation problems noted elsewhere):
Your first loop, "for (; n > 0;)", is strange because you're printing the entire number n into the buffer at counter. So why would you need to do this more than once? If you were selecting individual digits you might, but you're not, and obviously you know how to do this because you already used "sprintf(charIt, "%d", giveStr);". [Aside: giveStr isn't a great name for an unsigned integer variable!]
Your second loop also has strange conditions: you set counter to 0, set the condition that counter > 0, and then decrease counter inside. This obviously isn't going to loop over the characters in the way you want. Assuming you thought the first loop was character-by-character, then maybe you were thinking to loop down from counter-1 to 0?