Basically I have a function called MinSubTab that is supposed to calculate the sum of the array passed and also to change the value passed in the first argument from inside the function without using return. This is done with pointers. Anyway, I think it'd be easier if I just showed you the code so here it is:
maintab.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "tab.h"
int main(){
int *reftab;
int min;
reftab = (int *)malloc(sizeof(int) * NMAX);
InitTab(reftab,NMAX);
printf("\n Total: %d et min: %d", MinSumTab(&min, reftab, NMAX), min);
free(reftab);
return 0;
}
tab.c
void InitTab(int *tab, int size){
srand(time(NULL));
for (int i=0; i<size; i++){
*(tab+i) = rand() % 10;
}
}
int MinSumTab(int *min, int *tab, int size){
int total=0;
int minimum = NMAX;
int temp = *min;
for (int i=0; i<size; i++){
total += *(tab+i);
}
for (int i=0; i<size; i++){
if(*(tab+i)<minimum){
minimum = *(tab+i);
}
}
*min = minimum;
return total;
}
So the expected result here is that the sum is printed (which it is) and the minimum value of the array is printed (which it is not). Every single time the min variable equals 8 and I've no idea how to actually change the value of min from within that function.
Please help as my brain has no more capacity for rational thought, it's been 1.5 hrs and no solution in sight. Thanks
Looks like a small mistake:
You initialize minimum with NMAX, which I assume is 8 (the size of the array). 99.9% of the random numbers will be bigger. So 8 is chosen as the minimum.
What you really want is to initialize it with RAND_MAX – the maximum value rand() can return.
In C order of evaluation and argument passing is undefined.
You can of course the order yourself but it only to feed your curiosity.
#include <stdio.h>
volatile char *message[] = {
"fisrt", "second", "third", "fourth"
};
int print(size_t x)
{
printf("%s\n", message[x]);
return x;
}
int main()
{
printf("%d %d %d %d\n", print(0), print(1), print(2), print(3));
return 0;
}
Note. There is one exception from this rule.
Logical operators are evaluated form the left to the right.
if( x != NULL && *x == 5)is safe because x will not be dereferenced if it is NULL
Related
I am relatively new to C. My program is supposed to fill in the array with random numbers and i have to find the max and min using 1 function. The program works fine up until the point i have to return the values my 2 pointers get from the function. When i go to print them the porgram stop working and exits with the return value of 3221225477. I have been trying to fix this for 3 hours and i am going INSANE. Please help in any way you can i would really apreciate it.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void MaxMin(int size, int *B, int *Max, int *Min);
int main(int argc, char *argv[])
{
int N, i,*A,*MAX,*MIN;
srand(time(NULL));
/*Making sure the user enters a proper value for the array*/
do
{
printf("Give the number of spaces in the Array\n");
scanf("%d",&N);
}
while(N<1);
A = (int *) malloc(N*(sizeof(N)));
/*Giving random numbers to the array and printing them so i can make sure my code is finding the max min*/
for(i=0;i<N;i++)
{
A[i]=rand()%100;
printf("\n%d\n",A[i]);
}
/*Calling my void function so that the pointers MAX and MIN have a value assigned to them */
MaxMin(N, A, MAX, MIN);
/*Printing them*/
printf("\nMax = %d\nMin = %d",*MAX,*MIN);
free(A);
return 0;
}
/*The function*/
void MaxMin(int size, int *B, int *Max, int *Min)
{
/*using 2 temporary ints to get max min cause pointers and arrays confuse me*/
int max=B[0],min=B[0],i;
for(i=1;i<size;i++)
{
if(max<B[i])
{
max = B[i];
}
if(min>B[i])
{
min = B[i];
}
}
/*These have the proper value last i chekced */
Max = &max;
Min = &min;
}
(edit) SOLUTION Ty so much for the help !
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void MaxMin(int size, int *B, int *Max, int *Min);
int main(int argc, char *argv[])
{
int N, i,*A,MAX ,MIN ;
srand(time(NULL));
/*Making sure the user enters a proper value for the array*/
do
{
printf("Give the number of spaces in the Array\n");
scanf("%d",&N);
}
while(N<1);
A = (int *) malloc(N*(sizeof(int)));
/*Giving random numbers to the array and printing them so i can make sure my code is finding the max min*/
for(i=0;i<N;i++)
{
A[i]=rand()%100;
printf("\n%d\n",A[i]);
}
/*Calling my void function so that the pointers MAX and MIN have a value assigned to them */
MaxMin(N, A, &MAX, &MIN);
/*Printing them*/
printf("\nMax = %d\nMin = %d",MAX,MIN);
free(A);
return 0;
}
/*The function*/
void MaxMin(int size, int *B, int *Max, int *Min)
{
*Max=B[0];
*Min=B[0];
int i;
for(i=1;i<size;i++)
{
if(*Max<B[i])
{
*Max = B[i];
}
if(*Min>B[i])
{
*Min = B[i];
}
}
}
You passed to the function MaxMin pointers MAX and MIN by value. That is the function deals with copies of (indeterminate) values of the passed pointers. Changing the copies does not influence on the original arguments.
Within main you should declare MIN and MAX as objects of the type int.
int N, i,*A, MAX, MIN;
and call the function ,like
MaxMin(N, A, &MAX, &MIN);
Within the function you should write
*Max = &max;
*Min = &min;
And at last in main you should call printf like
printf("\nMax = %d\nMin = %d", MAX, MIN);
Pay attention to that the expression sizeof( N ) used in this statement
A = (int *) malloc(N*(sizeof(N)));
is error prone. The type of the variable N can be changed for example from the type int to the type size_t. In this case the size of the allocated memory will be incorrect, You should write for example
A = (int *) malloc(N*(sizeof( *A )));
You have three bugs:
In main, you don't assign MAX or MIN any values. So you pass garbage to MaxMin.
In MaxMin, Max and Min are about to go out of scope. Changing their values before they go out of scope has no effect on anything.
In main, you don't create any place to hold the maximum and minimum values. So where are you expecting them to be stored?
I'm trying to create a function that returns as its result the sum of the elements in the array. When I try to run the program, I get a segmentation fault. Could someone please point me in the right direction? Thank you!
int arraySum (int array[], int numberOfElements) {
int result = 0;
for (int i = 0; i < numberOfElements; i++)
{
result += array[i];
}
return result;
}
int main (void) {
int numberOfElements;
int *array = NULL;
printf("How many elements would you like in your array: ");
scanf("%i", &numberOfElements);
printf("\nPlease list the values of the elements in the array: ");
for (int i = 0; i < numberOfElements; i++)
{
scanf("%i", &array[i]);
}
int result = arraySum(array, numberOfElements);
return result;
}
The problem you have is, that in C you need to manually allocate the memory if you are using a pointer instead of say a fixed-size array.
This is usually done by calling malloc, which will return a void-pointer (void*), which you need to cast to the desired type (in your case (int*)) before assigning it.
It is also important to note, that, when using malloc, you need to specify the amount of Bytes you want to allocate. This means that you can't just call it with the number of integers you want to store inside, but rather have to multiply that number with the amount of Bytes that one integer occupies (which depends on the Hardware and Operating System you use, hence you should use sizeof(int) for that purpose, which evaluates to that size at compile time).
I modified your code with a working example of how it could be done:
#include <stdio.h>
#include <stdlib.h>
int arraySum (int array[], int numberOfElements) {
int result = 0;
int i;
for (i = 0; i < numberOfElements; i++) {
result += array[i];
}
return result;
}
int main(int argc, char **argv) {
int numberOfElements;
int *array = NULL;
printf("How many elements would you like in your array: ");
scanf("%i", &numberOfElements);
array = (int*) malloc(numberOfElements * sizeof(int));
printf("\nPlease list the values of the elements in the array: ");
int i;
for (i = 0; i < numberOfElements; i++) {
scanf("%i", &array[i]);
}
int result = arraySum(array, numberOfElements);
printf("\n\nThe result is: %d\n", result);
return 0;
}
You are also trying to return the result in your main function, but the return value of main in C is used to signal whether your program terminated without errors (signalled by a return value of 0) or didn't encounter any issues (any value other than 0).
You need to allocate memory. It is not enough to just declare a pointer. You do it like this: array=malloc(numberOfElements*sizeof(*array));
Also, although it is possible to return result from the main function, you should not do that. The return value from main is usually used for error checking. Change the end of your program to
printf("Sum: %d\n", result);
return 0;
Returning 0 usually means that no error occurred.
The code runs until it reaches the statement:
printf("%d", sumOccur(input));
The code:
#include <stdio.h>
#include <stdlib.h>
int sumOccur(int A[]);
int main(){
int input[6] = {1,1,1,2,2,3};
printf("%d", sumOccur(input));
return 0;
}
int sumOccur(int A[]) {
int sum, i;
while(A[i]!='\0'){
sum += A[i];
i++;
}
return sum;
}
If I have made any silly mistakes please oblige.
It's not the printf() crashing. It's sumOccur(). Your array has no \0 value in it, so your while() never terminates and you end up in a near-infinite loop and run off the end of the array.
The array is an array of numbers, not a string, so there is no reason whatsoever to think there there would be a null-terminator on the values. null terminators are for strings, not arrays of numbers.
In your function int sumOccur you have two problems-
1. sum and i are not initialized just declared. Initialize both to 0 .
2. Also while(A[i]!='\0') ain't going to work as expected as your array doesn't have that value in it.
Your code invokes undefined behaviour: you access A[6] and subsequent inexistent entries in sumOccur trying to find a final 0 in the array, but you do not put one in the definition of input in the main function.
-------- cut here if you are not interested in gory implementation details --------
The array is allocated on the stack, very near the top since it is instantiated in the main function. Reading beyond the end until you find a 0 likely tries to read beyond the end of the stack pages and causes a segmentation fault.
Note that you are dealing with an int array,which means it normally won't contain '\0' character.To iterate over the array you need to specify number of elements.Here is the correct way :
#include <stdio.h>
#include <stdlib.h>
int sumOccur(int A[],size_t number_of_elemets);
int main(){
int input[6] = {1,1,1,2,2,3};
//Get the number of elements
size_t n = sizeof(input) / sizeof(int);
printf("%d", sumOccur(input,n));
return 0;
}
int sumOccur(int A[],size_t number_of_elements) {
int sum = 0;
size_t i = 0;
while( i < number_of_elements )
{
sum += A[i];
i++;
}
return sum;
}
You are iterating while A[i] != '\0' but there is no '\0' in the array and also you never initialize sum which is unlikely the cause for a crash but it could be.
You need to pass the number of elements in the array, like this
#include <stdio.h>
#include <stdlib.h>
int sumOccur(size_t count, const int *A);
int sumOccurCHQrlieWay(const int *A, size_t count);
int main()
{
int input[] = {1, 1, 1, 2, 2, 3};
printf("%d", sumOccur(sizeof(input) / sizeof(*input), input));
return 0;
}
int sumOccur(size_t count, const int *A)
{
int sum;
sum = 0;
for (size_t i = 0 ; i < count ; ++i)
sum += A[i];
return sum;
}
int sumOccurCHQrlieWay(const int *A, size_t count)
{
return sumOccur(count, A);
}
could everyone please help me what is wrong with my code or what is missing from my code...
We have this activity where we have to find the highest number using another function..
#include <stdio.h>
#include <stdlib.h>
#define p printf
#define s scanf
int high (int n1);
int main(int argc, char *argv[])
{
int i, num[10];
p("Input 10 numbers\n");
for (i=0; i<10; i++)
{
p("Enter Number: ");
s("%d",&num[i]);
}
p("Highest Number: %d",high(num[i]));
getch();
}
int high (int n1)
{
int l;
for (l=0; l<n1; l++)
{
if (n1 > l)
return n1;
}
}
When I input any number I always got 37..
int high (int n1); should be
int high (int *arr, int sz); /* You need to pass an array */
p("Highest Number: %d",high(num[i])); should be
p("Highest Number: %d",high(num, 10)); /* Passing array now, not one element */
int high() should be re-written as:
int high (int *arr, int sz)
{
int l, mx = INT_MIN;
for (l=0; l<sz; l++)
{
if (mx < arr[l])
{
/* Left as an excercise */
}
}
return mx;
}
As this is tagged c++, I would suggest using available C++ to find max in a range:
const int max = *std::max_element(&num[0], &num[10]); // #include <algorithm>
Well, I don't know if you still need an answer, but I corrected your code. Here are the mistakes I found
int high (int n1)
{
int l;
for (l=0; l<n1; l++)
{
if (n1 > l)
return n1;
}
}
In this for-loop, there is the condition l<n1 and inside the for loop you have the statement if(n1 > l) which will never be attained because of l<n1. You said you were getting 37 each time, but I was getting 10 instead. This shows it was undefined behavior because no real value was returned. ( This code part really didn't mean any sense either as this function doesn't even try to find the largest number ).
Another issue I found is you have used getch() without including <conio.h> ( Also pointing out that <conio.h> is not standard in C++ )
Well, even though this question is tagged C++, since the code is completely c, I have made a fixed code in c. I've removed getch() in the code. So here is the code
#include<limits.h>
#include <stdio.h>
#include <stdlib.h>
#define p printf
#define s scanf
int high (int *n1,int lar); // now I have used *n1 to get the address of the array.
int main(int argc, char *argv[])
{
int i, num[10],lar=INT_MIN; // the variable lar is given the minimum value that can be held by an int
p("Input 10 numbers\n");
for (i=0; i<10; i++)
{
p("Enter Number: ");
s("%d",&num[i]);
}
p("Highest Number: %d",high(num,lar)); // sending the entire array to the function by sending its address
}
int high (int *n1,int lar)
{
int l;
for (l=0; l<10; l++) // since the size you have taken for your array is 10, I have used 10 here. But if you don't know the size beforehand, pass the size as an argument to the function
{
if (n1[l] >lar ) // Well, this is the simple part
lar=n1[l]; // Simply assigning the largest value to lar
}
return lar; // Finally returning the value lar.
}
Well, hope this helps you.
can someone please help me figure out what i'm doing wrong here? i'm getting inaccurate results here. I seem to be getting the first value in the array each time and i cant seem to figure out what i'm doing incorrectly
#include <stdio.h>
int getbillsum ( int price[] );
int main( void )
{
int itemprice [10];
int total = 0;
for (int c=0;c <10;c++ ) //Looping to get item prices
{
printf ("\nEnter the price of the item: ");
scanf (" %d", &itemprice[c]);
}
total = getbillsum (itemprice);
printf ("%d", total);
return 0;
}
int getbillsum (int price []) //function to sum the values in array
{
int sum = 0;
for (int i=0; i<sizeof(price); i++)
{
sum+=price[i];
}
return sum;
}
You can't pass arrays to functions in C (well, not as an array anyway). Arrays decay into pointers, the sizeof which is always the same (4 for 32 bit systems, 8 for 64 bits).
For more information see paragraph 2.3 here.
The easiest, most common and most reliable way of solving your issue is to pass the length of the array as a second argument:
int getbillsum (int *price, size_t len)
{
int sum = 0;
for (int i=0; i<len; ++i)
sum += price[i];
return sum;
}
//usage
int main ( void )
{
int price[10];
for(int i=0;i<10;++i)
scanf(" %d", &price[i]);
printf("Sum: %d\n", getbillsum(price, sizeof(price)/sizeof(*price)));
return 0;
}
You also had a problem in your code: you added the return statement inside of your loop.
Just a quick-tip: The sum of an array of ints is not unlikely to be too much for a single int to hold, so I'd change the return-type of getbillsum to long, too
I've also edited your question, addressing quite a lot of issues considering how short your code was:
int getbillsum ( price );//missing type, changed to
int getbillsum ( int price[] );//better would be int getbillsum ( int *price ); but considering your question, left it as array
scanf ("%d", &itemprice[c]);//unsafe, changed it to
scanf (" %d", &itemprice[c]);//add space
total = getbillsum (itemprice,9);//why the second param?
total = getbillsum (itemprice);//to match function prototype
return sum;//moved OUTSIDE of the loop...
sizeof(price) does not give you the length of the array, but the size of the pointer (int price[]), which is probably 4. Also, you immediately return in the first for run. Put return outside the for loop.
You do fix it by supplying the array size, but you never use it. Update your getbillsum function:
int getbillsum (int price [], int length) //function to sum the values in array
{
int sum = 0;
for (int i=0; i<length; i++)
{
sum+=price[i];
}
return sum;
}
In addition to posted answers, you can consider a technique suggested in this answer.
Edit Quoted from comment
it's non-standard, dangerous (think of overflow, forgetting to
dereference at the correct offset and the like), and you should not
try this
In your case it will be something like that :
void *p = calloc(sizeof(itemprice) + sizeof(unsigned long int),1));
*((unsigned long int*)p) = 10;
quote from linked answer
n is now stored at ((unsigned long int)p)
Your getbillsum will look like that now (did not compile it, consider it as pseudocode)
int getbillsum (void* p)
{
int* price = p+sizeof(unsigned long int);
unsigned long int size = *p;
int sum = 0;
for (int i=0; i<size; i++)
{
sum+=price[i];
}
return sum;
}