still new to algorithms in general, started with c, but stuck with the error segmentation fault couldn't really know whats the exact problem.
#include <stdio.h>
int main()
{
int i,nb;
float T[nb][2];
printf("how many mesures?\n");
scanf("%d",&nb);
for(i=0;i<nb;i++)
{
printf("whats the temperature T%d ?\n",i);
scanf("%f",&T[i][0]);
printf("whats the humidity H%d ?\n",i);
scanf("%f",&T[i][1]);
}
return 0;
}
This declaration of a variable length array
{
int i,nb;
float T[nb][2];
has undefined behavior because the variable nb is not initialized and has an indeterminate value. You have to declare the array after assigning a positive value to the variable nb.
int main()
{
int i,nb;
printf("how many mesures?\n");
scanf("%d",&nb);
float T[nb][2];
//...
Related
I am trying to write a program that, when given a certain price, will break it into 20s, 10s, 5s and 1s.
However, I am getting the following error: EXC_BAD_ACCESS (code=1, address=0x0)
The error shows up on the line: *tens=diff in the function.
I do not understand what is wrong!
Here is the code:
#include<stdio.h>
#include<stdlib.h>
void pay_month(int , int *, int *, int *, int *);
int main(){
int dollars, *twenties=0, *tens=0, *fives=0, *ones=0;
printf("enter amount to pay: ");
scanf("%d",&dollars);
pay_month(dollars, twenties, tens, fives, ones);
return 0;
}
void pay_month(int dollars, int *twenties, int *tens, int *fives, int
*ones){
int diff=0;
int odolls;
odolls=dollars;
while(dollars%20!=0){
dollars=dollars-1;
diff++;
}
*tens=diff;
*twenties=dollars/20;
diff=0;
while(*tens%10!=0){
*tens=*tens-1;
diff++;
}
*tens=*tens/10;
*fives=diff;
diff=0;
while(*fives%5!=0){
*fives=*fives-1;
diff++;
}
*ones=diff;
diff=0;
while(*ones%1!=0){
*ones=*ones-1;
diff++;
}
printf("in %d there is %d twentis %d tens %d fives and %d ones\n",odolls, *twenties, *tens, *fives, *ones);
}
You are dereferencing a NULL pointer. That is, you are asking the computer to write into memory location 0. You are not allowed to do that.
I think what you've done is used pointers without quite understanding how to obtain them. Possibly just to stop the compiler from throwing errors.
This simple change should solve the problem:
int dollars, twenties=0, tens=0, fives=0, ones=0;
printf("enter amount to pay: ");
scanf("%d",&dollars);
pay_month(dollars, &twenties, &tens, &fives, &ones);
Notice that none of the values in the calling function are pointers anymore. They're just integers. You prefix with & when passing them to pay_month. That's the reference operator, which obtains a pointer to where the value is stored.
Now, when you dereference the tens pointer inside pay_month, you're actually accessing the same part of memory where the value tens is stored on the stack in main.
a classic case of pointers and variables
essentially when you are declaring pointer as
int *twenties=0, *tens=0, *fives=0, *ones=0;
you are essentially making these pointers to point to NULL memory which means no memory is allocated to those.
one way to solve this is by declaring these as variables and passing the address of these variables
int dollars, twenties=0, tens=0, fives=0, ones=0;
and
pay_month(dollars, &twenties, &tens, &fives, &ones);
I am trying to use scanf() to input values to a structure using pointers.Can you help me to understand why my code is not working
This is my code:
#include<stdio.h>
struct student
{
int no;
float marks;
}st[2],*s;
main()
{
printf("enter the values");
for(s=st;s<st+2;s++)
{
scanf("%d%d",&s->no,&s->marks);
}
for(s=st;s<st+2;s++)
{
printff("%d\t%d\t",s->no,s->marks);
}
}
in this code scanf is not working properly,it is taking only the first value
You are using the wrong format specifier. %d is used for ints while %f is used for floats. Use
scanf("%d%f",&s->no,&s->marks);
and
printf("%d\t%f\t",s->no,s->marks);
instead as s->marks is a float, not an int. Using the wrong format specifier leads to Undefined Behavior.
#include<stdio.h>
struct student
{
int no;
float marks;
}st[2],*s;
main()
{
printf("enter the values");
for(s=st;s<st+2;s++)
{
scanf("%d%f",&s->no,&s->marks);
}
for(s=st;s<st+2;s++)
{
printf("%d\t%f\t",s->no,s->marks);
}
}
U have to use %f for float
In the structure you have taken two variable one is int type and other is float type but while doing scanf(taking input) you are doing %d for float whereas it should be %f for float .This is a very minor mistake but you should try to avoid it on your own by just looking at your code carefully :)
Happy coding
i have written this code for a question on codechef (A4)....when i give the input:
2
4 2
This program stops unexpectedly without taking further input ....can some please point out the mistake in the code?
#include <stdio.h>
#include<math.h>
void number(long int a,int b)
{
int c;
c=b;
int first[c],last[c],e=1,i;
long int d;
d=pow(a,a);
for(i=(c-1);i>=0;i--)
{
last[i]=fmod(d,pow(10,e));
e++;
}
e=1;
while(d>pow(10,(b-1)))
d/=10;
for(i=(c-1);i>=0;i--)
{
first[i]=fmod(d,pow(10,e));
e++;
}
for(i=0;i<c;i++)
printf("%d",first[i]);
printf(" ");
for(i=0;i<c;i++)
printf("%d",last[i]);
printf("\n");
}
int main()
{ int T;
scanf("%d",&T);
while(T--)
{ long int a;
int b;
scanf("%ld %d",a,b);
number(a,b);
}
return 0;
}
scanf("%ld %d",&a,&b);
Using uninitialized variables lead to UB. You should use &a and &b to scan variables
In your code you have
scanf("&ld %d",a,b);
It means you're trying to input integers to the memory locations of values of a and b. For and example let value of a = 1234566466 (long int), and b = 1234 (int). Accordingly 1234 is a memory location which is at the start of the RAM. Tn that area System files are loaded. So you are going to change system behaviour. That is not allowed.
Further when the complier allocate some memory space to your program, you can access only the memory which is inside your memory segment directly. But above statement trying to access another segment.
That's why you get segmentatin fault.
You are passing an integer to a function that expects a pointer, for scanf the "%d" and "%ld" specifiers expect int * and long int * respectively, and you pass int and long int, so when trying to access the integers as if they were memory addresses the segmentation fault occurs.
The correct way to call scanf would be as Gopi said
scanf("%ld %d", &a, &b);
there you pass a and b addresses instead of their values.
Write a program to manipulate the temperature details as given below.
- Input the number of days to be calculated. – Main function
- Input temperature in Celsius – input function
- Convert the temperature from Celsius to Fahrenheit.- Separate function
- find the average temperature in Fahrenheit.
how can I make this program without initial size of array ??
#include<stdio.h>
#include<conio.h>
void input(int);
int temp[10];
int d;
void main()
{
int x=0;
float avg=0,t=0;
printf("\nHow many days : ");
scanf("%d",&d);
input(d);
conv();
for(x=0;x<d;x++)
{
t=t+temp[x];
}
avg=t/d;
printf("Avarage is %f",avg);
getch();
}
void input(int d)
{
int x=0;
for(x=0;x<d;x++)
{
printf("Input temperature in Celsius for #%d day",x+1);
scanf("%d",&temp[x]);
}
}
void conv()
{
int x=0;
for(x=0;x<d;x++)
{
temp[x]=1.8*temp[x]+32;
}
}
In C arrays and pointers are closely related. In fact, by design an array is just a syntax convention for accessing a pointer to an allocated memory. *(see note for more details below)
So in C the statement
anyarray[n]
is the same as
*(anyarray+n)
Using pointer arithmetic.
You don't really have to worry about the details to make it "work" as it is designed to be somewhat intuitive.
Just create a pointer, and allocate the memory and then access it like as an array.
Here is some examples --
int *temp = null; // this will be our array
// allocate space for 10 items
temp = malloc(sizeof(int)*10);
// reference the first element of temp
temp[0] = 70;
// free the memory when done
free(temp);
Remember -- if you access outside of the allocated area you will have unknown effects.
To be clear it is the indexing operator ([ ]) that is translated to pointer arithmetic. This is not an array in the modern sense of the
type. Whether (or not) the pointer involved points to (dynamically) allocated
memory is inconsequential to how this operator works. In a more modern language you would be able to operate on the array as an abstract type (to see how big it is, for example), you can't do this in C.
An array without an initial size is basically just a pointer. In order to dynamically set the size of the array, you need to use the malloc() or calloc() functions. These will allocate a specified amount of bytes of memory.
In your code above, declare temp as an int pointer
int *temp;
Then allocate space for it using malloc() or calloc(). The argument that these functions take is is the number of bytes of memory to allocate. In this case, you want enough space for d ints. So...
temp = malloc(d * sizeof(int));
malloc returns a pointer to the first byte in the block of memory that was just allocated. Regular arrays are simply pointers to the first byte in a sectioned off block of memory, which is exactly what temp is now. Thus, you can treat the temp pointer as an array! Like so:
temp[1] = 10;
int foo = temp[1];
printf("%d", foo);
Outputs
10
You will need to declare temp as an int pointer (instead of an int array). Then, you can use malloc in your main (after your first scanf):
temp = malloc(d * sizeof(int));
If your compiler supports c99, then simply use VLA(variable length array).Use like this:
void input(int);
int d;
void main()
{
int x=0;
float avg=0,t=0;
printf("\nHow many days : ");
scanf("%d",&d);
int temp[d];
input(d);
conv();
for(x=0;x<d;x++)
{
t=t+temp[x];
}
avg=t/d;
printf("Avarage is %f",avg);
getch();
}
Now temp[] is defined inside main() after date input.
1-add #include<stdlib.h> at the top of your file. Then modify the conv() code as follows:
2- modify temp declaration as follows (global variable):
int *temp;
3- modify input(int d) function as follows (tested on Visual Studio 2010):
void input(int d)
{
int x=0;
temp=(int*)malloc(sizeof(int)*d);
for(x=0;x<d;x++)
{
printf("Input temperature in Celsius for #%d day",x+1);
scanf("%d",&temp[x]);
}
}
Allocate the "array" dynamically on the heap after you read the size.
I didn't change anything else so you may see it clearly.
#include<stdio.h>
#include<conio.h>
#include <stdlib.h> //here
void input(int);
int *temp=0; //here
int d;
void main()
{
int x=0;
float avg=0,t=0;
printf("\nHow many days : ");
scanf("%d",&d);
temp=malloc(d * sizeof(int)); //here
input(d);
conv();
for(x=0;x<d;x++)
{
t=t+temp[x];
}
avg=t/d;
printf("Avarage is %f",avg);
getch();
}
void input(int d)
{
int x=0;
for(x=0;x<d;x++)
{
printf("Input temperature in Celsius for #%d day",x+1);
scanf("%d",&temp[x]);
}
}
void conv()
{
int x=0;
for(x=0;x<d;x++)
{
temp[x]=1.8*temp[x]+32;
}
}
Maybe it's late to answer but...
If you work with small embedded system you might not have malloc and free functions.
So you have to sacrifice memory for 366 * sizeof(your_type), define it statically and use as a circular buffer. Then you can always slice it by number of days you need to calculate an average value.
Of course this makes natural constrains. You can define it by yourself.
I am trying to do my homework here, which is writing a program, that shows the distances to (0,0) of a certain number of points. However for some reason(s) as soon as my program starts, windows says that it has stopped working. I tried it with two different compilers, and they don't give me any error messages.
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
struct point {
int x;
int y;
};
struct point getPoint();
void printPoint(struct point);
double distanceToO(struct point p);
void createArray(struct point, int);
int main() {
int number, i;
struct point coord[number];
printf("Type the number of points you want to create: ");
scanf("%d", &number);
printf("\n\n");
for(i=0;i<number;i++)
coord[i]=getPoint();
printf("\n\t\tPoint\tDistance to (0,0)\n");
for(i=0;i<number;i++) {
printPoint(coord[i]);
printf("\t%0.2lf", distanceToO(coord[i]));
}
system("pause");
return 0;
}
struct point getPoint() {
struct point p;
printf("Type the x and the y-value for a point with a space in between: ");
scanf("%d %d", &p.x, &p.y);
return p;
}
void printPoint(struct point p){
printf("\n\t\t(%d,%d)",p.x,p.y);
}
double distanceToO(struct point p) {
return sqrt((0-p.x)*(0-p.x)+(0-p.y)*(0-p.y));
}
That is what's to do in detail:
Write a Program, that first asks how many points should be created, and then asks the user for the x and y values of the points.
Then the Program should give out a table, showing the Point and the distance to (0,0).
The following functions have to be created/used:
"point getpoint()" - which asks to enter the coordinates
"void printpoint(point p)" - which prints the coordinates of the points
"double distanceToO(point p)" - returns the distance to (0,0)
Create a structure point, that has two members the x-coordinate and the y-coordinate of a point.
Can somebody give me a hint on what's wrong?
int number, i;
struct point coord[number];
number has not been initialized, and you are using it to declare the size of the coord array. You will be generating an array of effectively random size on the stack, which may well cause a crash.
The variable number is uninitialized when used to specify the number of elements in the array coord. The array is then accessed and it is not known how many elements are in they array. Read a valid value into number before using it and check that a valid value has definitely been read:
/* scanf() returns number of assignments made. */
if (scanf("%d", &number) == 1)
{
}
Always check the result of input operations to ensure subsequent code is processing variables with valid values.
int number;
struct point coord[number];
I don't see where number is initialized. If you really want to use VLA, you should declare coord afterwards:
int number;
scanf("%d", &number);
struct point coord[number];
Otherwise, since number has an automatic storage duration, its value will be undefined.
I'm pretty surprised you don't get a warning/error on this:
int number, i;
struct point coord[number];
You allocate an array of struct point with a size equal to an unitialized variable.
Note that if you use Visual Studio, it doesn't fully support C99 standard either so it's not allowed to have statements before declarations, as in:
int number;
number = some_number;
struct point coord; // Error, you have a statement above