I'm trying to write a simple program that'll prompt the user to enter N numbers, store them in an array, then just sum them all up
I understand I can just do this with a recursion but I'm trying to learn how array works
Example:
1 (hit enter)
2 (hit enter)
...
10 (hit enter)
Expected output: 55
#include <stdio.h>
int main (void){
int n;
int a[n];
int counter;
printf("How many numbers do you want to enter? \n");
scanf("%d", &n);
printf("OK! now enter your number: \n");
for (int i = 0; i <= n; i++){
scanf("%d", &a[i]);
counter =+ a[i];
}
printf("The answer is: %d\n", counter);
return 0;
}
Right now there's no error message, no output, just the standard windows error message
"scanner.exe has stopped working..."
I'm using Win8 and GCC compiler
First of all, you can't create an static array without first knowing its size. You first need to ask the user for the "n" variable and then declare your array.
You also need to explicitly initialize your counter variable to be zero before you start counting. In C, variables don't default to 0 when you declare them.
The operator "=+" doesn't exist AKAIK, change it to "+=".
Last but not least, the limit in your loops is a little off, you're asking for 11 values ;)
(I edited this post, I was wrong about only asking for 9 values. I tend to confuse that sort of stuff)
#include <stdio.h>
int main (void){
int n;
int counter = 0;
printf("How many numbers do you want to enter? \n");
scanf("%d", &n);
int a[n];
printf("OK! now enter your number: \n");
for (int i = 0; i < n; i++){
scanf("%d", &a[i]);
counter += a[i];
}
printf("The answer is: %d\n", counter);
return 0;
}
You are using variable length arrays. At run time the value of n must be known. Place the declaration
int a[n];
after taking input for n, i.e, after scanf("%d", &n); and initialize counter to zero before using it otherwise you will get garbage value (because of undefined behavior).
Also change the for loop condition from i <= n to i < n.
After this line:
int n;
What do you think the value of n is?
Now go to the next line:
int a[n];
How big is this array?
Can you access it properly?
Related
I was writing a C program to find inversions in an array. The program compiles smoothly but as soon as I run it, it displays a garbage value where I take the array as a input. The program is given below:
#include <stdio.h>
#include <stdlib.h>
int checkInversions(int arr[], int n) {
int i, j, inverse_count = 0;
for (i = 0; i < n - 1; i++) {
for (j = i + 1; j < n; j++) {
if (arr[i] > arr[j]) {
inverse_count++;
}
}
}
return inverse_count;
}
int main() {
int arr[10], i, n;
printf("Enter the elements of the array: %d");
for (i = 0; i <= 10; i++) {
scanf("%d", &arr[i]);
}
n = sizeof(arr) / sizeof(arr[0]);
printf("\n The inverse is: %d", checkInversions(arr, n));
return 0;
}
Now, when the statement Enter the elements of the array: is displayed, just beside that is a garbage value like 623089. I am able to take the input but the result is not correct. What is the cause of this? Any help in this regard will be appreciated.
You are calling printf with a format specifier for %d and nothing passed to satisfy the variable expected by the format string. This is undefined behavior.
What you meant to do was merely:
printf("Enter the elements of the array: ");
Also, since arr has 10 elements, you iterate through it as such:
for(i = 0; i < 10; i++)
You don't need to use sizeof to determine the size of the array since you already know it; it's 10.
I think you are missing the variable that should populate the %d on the printf.
Try taking out the %d on the printf call so it ends up like:
printf("Enter the elements of the array: ");
Or assign the corresponding variable to display with that "%d", like this:
printf("Enter the elements of the array: %d", variable);
Check if that helps!
Your problem is printf("Enter the elements of the array: %d");. You tell the program that you want to print an integer, but you do not specify which integer that is. Remove the %d and the garbage value will be gone, like this: printf("Enter the elements of the array: ");
I'm writing a program that requires me to do a union of two arrays. Here is my code so far.
I get Segmentation fault as an error after I enter set A.
#include <stdio.h>
void Union(int a[], int b[], int set1, int set2)
{
int u[20], i, j, unionIndex=0,trigger;
for(i=0; i<set1; i++)
{
u[unionIndex] = a[i];
unionIndex++;
}
for(i=0; i<set2; i++)
{
trigger=0;
for(j =0; j<set1; j++)
{
if(b[i] == u[j])
{
trigger =1;
break;
}
}
if(trigger =0)
{
u[unionIndex]=b[i];
unionIndex++;
}
}
for(i=0;i<unionIndex;unionIndex++)
{
printf(" %d",u[i]);
}
}
int main(void) {
int N=0;
int M=0;
int i;
int j;
printf("Please enter the number of elements in set A: ");
scanf("%d",N );
int a[N];
printf("Enter the numbers in set: ");
for(i=0;i<N;i++)
{
scanf("%d",&a[i]);
}
printf("Please enter the number of elements in set B: ");
scanf("%d",M );
int b[M];
printf("Enter the numbers in set: ");
for(j=0;i<M;i++)
{
scanf("%d",&b[i]);
}
Union(a,b,N,M);
return 0;
}
I'm pretty sure the issue has something to do with arrays because the program will compile but i get the error right after the user enters set A. I'm a beginner at C but I know a lot more about Java, so I'm thinking this has something to do with memory allocation. I'm not really sure how to solve the issue, so if you could point me in the right direction that would be helpful.
You need to pass the address of the variable to scanf()
Change
printf("Please enter the number of elements in set A: ");
scanf("%d",N );
to
printf("Please enter the number of elements in set A: ");
scanf("%d", &N);
Same goes for other place
printf("Please enter the number of elements in set B: ");
scanf("%d", &M);
There is another possible mistake
Its here
for(j =0; j<set1; j++)
{
if(b[i] == u[j])
In this set1 is equal to N, so j will go from 0 to N-1. And array u[] has only 20 elements. There is a possibility of array access out of bound if some user enter value more then 20 for N.
The problem, as I see it is in
scanf("%d",N );
and
scanf("%d",M );
It invokes undefined behavior as scanf() needs the argument to a format specifier to be a pointer to the type.
Just to clarify, you're essentially passing the address as 0 (value of the variable), which is not a valid addres, anyway.
You need to pass the address there, like
scanf("%d", &N );
and
scanf("%d", &M );
That said, in your Union() function, you're using a user-defined value to limit the for loop, against a constant value 20. In case the user input is more than 20, you'll be overrunning the memory which invokes undefined behavior.
The reason you're getting the segmentation fault is because of how you're calling scanf when reading in N and M. The %d format specifier for scanf expects an int *, i.e. the address of an int, but you're passing in an int. This is undefined behavior.
So you can fix them like this:
scanf("%d",&N );
....
scanf("%d",&M );
Some addtional bugs:
When looping to read in the values for b:
for(j=0;i<M;i++)
{
scanf("%d",&b[i]);
}
You have the wrong loop indexes:
for(j=0;j<M;j++)
{
scanf("%d",&b[j]);
}
When checking trigger:
if(trigger =0)
This is an assignment, not a comparison:
if(trigger == 0)
When looping to print out u:
for(i=0;i<unionIndex;unionIndex++)
You're incrementing the wrong variable:
for(i=0;i<unionIndex;i++)
Finally, u need to have a length of at least set1 + set2, otherwise you risk writing off the end of the array:
int u[set1+set2];
Fix those and you should get the desired results.
C Programming Beginner.
I don't understand why this code doesn't work. The numbers I get as answers for min and max are 2686672 and 4525824. Can anyone explain please? Thank you.
#include <stdio.h>
int main(void) {
int array[20], i, x, y;
int max, min;
printf("Please enter number of integers to be checked\n");
scanf("%d", &x);
for (y = 0; y <= x; y++) {
printf("Please enter your numbers\n");
scanf("%d", &i);
}
min = array[0];
max = array[0];
for (y = 0; y <= x; y++) {
if (array[i] < min) {
min = array[i];
} else if (array[i] > max) {
max = array[i];
}
}
printf("%d is the min and %d is the max", min, max);
}
Your section at
for (y=0;y<=x;y++){
printf ("Please enter your numbers\n");
scanf ("%d",&i);
}
Has several issues. First, you're storing the value in i each time; that will get overwritten the next time through the loop. Second, you want < instead of <= as you will otherwise ask for too many numbers. (You should also check that the user asked for <= 20 numbers).
I think you want:
for (y=0;y< x;y++){
printf ("Please enter your numbers\n");
scanf ("%d",&array[y]);
}
You aren't storing the values that you read into i in your array when you have the loop asking for the numbers to be entered.
Later, your are indexing array with i, but the loop counter is y - so i is never changing (nor is it necessarily a valid index, since it holds the last value that was read via scanf).
Check your code again to make sure you actually store the values you read into an array, and then check what you are using for array indices when computing the max and min.
you are never storing the numbers into the array. You overwrite the number the user enters on each pass. You therefore end up with garbage data at the end, whatever happened to be initialized into max and min.
for (y=0;y<=x;y++){
printf ("Please enter your numbers\n");
scanf ("%d",&i);
array[y] = i;
}
at least this way there will be something in the array locations to compare with in your Max/Min Logic later on.
cheers.
write a loop to dump out the array after its entered - just so you can be sure you get the right stuff
for(i = 0 ; i < x; i++)
{
printf("%d\n", array[i];
}
Also (as others have said) your loop boundaries need to be < not <=. A 10 element array has elements numbered 0 - 9
To me, my program looks like it should do what I want it to do: prompt a user to enter 10 values for an array, then find the largest of those values in the array using a function, then return the largest number to the main () function and print it out.
But, when I enter values, I never get numbers back that look anything like the ones I'm entering.
For example, let's say I enter just "10, 11" I get back "1606416648 = largest value".
Does anyone know what I'm doing wrong?
Here's the code:
#include <stdio.h>
#define LIMIT 10
int largest(int pointer[]);
int main(void)
{
int str[LIMIT];
int max;
int i = 0;
printf("Please enter 10 integer values:\n");
while (i < LIMIT)
{
scanf("%d", &str[i]);
i++;
}
// Thanks for your help, I've been able to make the program work with the above edit!
max = largest(str);
printf("%d = largest value\n", max);
return 0;
}
int largest(int pointer[])
{
int i;
int max = pointer[0];
for (i = 1; i < LIMIT; i++)
{
if (max < pointer[i])
max = pointer[i];
}
return max;
}
scanf("%d", &str[LIMIT]); reads in one number and puts it in the memory location one past the end of your array.
After changes:
You don't need scanf() in your while condition; it should go in the while body instead.
Your scanf() still isn't quite right. You need to tell it where in the array you want to store the input.
str[i]; doesn't do anything.
printf("Please enter 10 integer values:\n");
scanf("%d", &str[LIMIT]);
This doesn't do what you think. First, it only reads one number in. Second, you are reading it into the last position + 1 of the array.
This program takes the first number in a file and indicates how many numbers are going to be after it, then does various other things with the numbers that follow.
It seems like scanf is causing an infinite loop when trying to read from the file. WHen I run the program not even the check at 1 works
Here is the code:
#include <stdio.h>
int main(void) {
int N, a, n;
int x=0;
int t=0;
printf("1"); //Check
scanf("%d", &N);
printf("2"); //Check
int nums[N];
int i;
printf("%d", &N); //Check
for (i=0; i<N; i++)
{
scanf("%d", &nums[i]);
t+=nums[i];
if (nums[i] > x) x=nums[i];
if (i=0 || nums[i] < n) n = nums[i];
}
a = t/N;
printf("Number Processed: \t%d\n", &N);
printf("Maximum: \t%d\n", &x);
printf("Minimum: \t%d\n", &n);
printf("Total: \t%d\n", &t);
printf("Average: \t%d\n", &a);
}
The way i run the program is
gcc -lab16
./a.out <in1
where in1 is text and has the numbers
7
6
-30
90
3903
-934
443
445
Thanks for your time.
if (i=0 || nums[i] < n) n = nums[i];
you are assigning i = 0, so the loop never realy advances! You probably wanted i == 0. This is causing the infinite loop.
Other issue: int nums[N]; - if you want an array of dynamic [determined in run-time] size, you will probably need to malloc() it.
Update: note that int nums[N] is valid in C99, so if your assigment is assuming C99 you should not worry about this issue. Otherwise - malloc() will be needed:
int* nums = (int*) malloc(sizeof(int) * N)
And don't forget to free(nums) before the program ends, or you will get memory leak.
if (i=0 || nums[i] < n) n = nums[i];
This is the culprit. You are making an assignment i=0 when you should do a comparison : i==0
Your loop goes to infinity because everytime you are i to 0.
Moreover, the code you gave us, gave me an error, because you were creating new variables during runtime.
#include <stdio.h>
#include "stdlib.h"
int main(void) {
int N, a, n;
int x=0;
int t=0;
int i;
int *nums;
printf("1"); //Check
scanf("%d", &N);
printf("2"); //Check
nums = malloc(N*sizeof(int));
....
There are numerous problems with this code.
You mistook assignment for comparison:
i=0
sets i to zero. You probably meant
i==0
which checks whether i is equal to zero.
You should check the value returned by scanf(). When data read by scanf() doesn't fit the format you specified it leaves the data in the buffer and the next call to scanf() sees the same data again.
The reason that the first printf() doesn't print anything is most likely that you are not printing any newline. Note that on some output devices like terminals output is line-buffered.
You are passing a pointer to a variable to printf(), but your format specifies %d. You probably meant the variable itself, not a pointer to it.
Also, if you need an array of length dependent on a value known only at runtime, you need to allocate it on the heap, e.g. using malloc().