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
Related
I have been attempting to wrap my head around an idea that I am certain is possible, I just am not sure if I am going about it in the right way. My intention is to create an array and then fill it with as many values as the user wants. However my goal is to not use any defined value per se. I would like to be able to continue increasing it the amount of values it can contain indefinitely.
This is the test code I have been using to try and figure this out:
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
int i;
int Up;
int Ary[0];
printf("Please enter the number of integers you want to input: ");
scanf("%d", &Up);
for(i = 0; i < Up; i++)
{
printf("Please enter a number: ");
Ary[i] = (int) malloc(sizeof(int));
scanf("%d", &Ary[i]);
}
for(i = 0; i < Up; i++)
{
printf("%d ", Ary[i]);
if(i % 10 == 0)
{
printf("\n");
}
}
return 0;
}
This may be a poor way of attempting to figure this out and I may also be doing this is a completely wrong way; However I get a segmentation fault sometimes. If I use small values such as only entering 4 or 5 values it works fine, however if I enter 10 values it gives me a segmentation fault. If I enter 50 values, it lets me enter all 50 but gives me a segmentation fault after printing out the 41st value.
The code itself is simply a means to an end. Ultimately what I would like to know is how I can set up an array of anything that can have values added to it indefinitely while retaining previous values using dynamic memory allocation?
PS. I hope this defines my question well enough, however if it does not I would like to refine my question so it is more clear. Please make a comment if this is unclear and why.
This isn't going to work:
int Ary[0];
You've made an array with no elements; the only valid use of such an array is to take its address, but you can't index into it as you have done.
Instead, you should make a pointer to what will later be allocated as an array:
int *Ary;
Then when you know how many integers you want:
Ary = malloc(Up * sizeof(int));
Now you can do Ary[index] for any index from 0 to (Up-1). If you later want to enlarge the array, you can use realloc() (many tutorials online for that).
You need to use dynamic allocation, what you are doing right now is static allocation, you need to learn how to use malloc and free.
So keep in mind that what you want to do is not "efficient" but can definitely be done as a learning exercise to learn how to make such a container.
What you need to do is allocate the amount of memory needed to contain the amount of values currently in your array +1 more value every time you want to "add" a new value to your array, for example: malloc(sizeof(int)*(<current_number_of_values>+1)).
I say "add" in quotes because what you will have to do is actually allocate memory for a brand new array every time and copy over your old values plus the new value the user enters and then free your old array to avoid memory leaks.
There are STL containers that do this internally but much more efficiently but I assume you are doing this to learn and not use your own containers for anything serious.
I have made a dynamic array of integers in C, here is my code
#include <stdio.h>
int main(){
int count=0, i, input;
int *myarr;
myarr=(int*)malloc(4*sizeof(int));
while(1){
scanf("%d", &input);
myarr[count]=input;
count++;
if (input == -1) break;
}
for (i=0; i<count; i++){
printf("%d ", myarr[i]);
}
return 0;
}
From the code, I thought i clearly made an array of 4 integers only i.e myarr[0] up to myarr[3], how come when i insert even 10 integers, it still prints all of them, it doesn't print garbage as i thought it would after the fourth integer... Maybe i didn't understand the point of dynamic creating an array?? Make me straight please!
You should only access myarr[0] up to and including myarr[3].
Accessing any other index is undefined behaviour: it might work, it might not.
Also, myarr[count]==input looks like a typo. Did you mean myarr[count] = input? The way you have it is testing if myarr[count] equals input. Technically the way you have it is undefined behaviour for any element of myarr since you are making use of uninitialised data.
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;
}
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
I am learning C language and I am facing a problem I don't seem to be able to resolve on my own.
I have a simple loop where I add up ascii values of all characters in each word.
char char_array[100];
int lexicographical_values[20];
int i, j = 0;
for( i = 0; i <strlen(char_array); i++) {
if(char_array[i] == ' ')
j++;
lexicographical_values[j] += (int)char_array[i];
}
Then, if I output the lexicographical_values array in a loop
printf("%d word is: %d \n", i, lexicographical_values[i]);
I get correct figures for each word (ex: dd = 200 and so on)
But if I actually look at each element's value in the array, I get big numbers that are far from being correct.
The question is, how do I get correct values and how does printf obtain the correct values?
Thanks
You have not initialized the lexicographical_values array. You can initialize it by doing:
int lexicographical_values[20] = {};
Every time you see big numbers in the output, check for uninitialized variables.
You're starting with uninitialized memory.
man memset
You have not initialized the char_array with anything, so most likely it has garbage (depends on compiler options and platforms) so, you do a strlen(char_array) and at this point we're not sure what we're going to get out of it. If you initialize it with 0s (like: char char_array[100] = {0}; then strlen will return 0 and you'll never enter the loop.
Maybe you're looking for sizeof() here?
Oh, yes, forgot to mention that you need to initialize the second array also as was already pointed out.