My Code does not print anything with gcc. I tried to flush the buffer, but does not make a difference.
#include <stdio.h>
int main() {
int foo[65];
for(int i; i < 64; ++i) {
printf("Number: Count: \n");
}
}
If remove the 3 line it works.
#include <stdio.h>
int main() {
for(int i; i < 64; ++i) {
printf("Number: Count: \n");
}
}
Is this a bug in gcc because this array is not related to the printf call.
Try switching your code to the following:
#include <stdio.h>
int main() {
int foo[65];
for(int i=0; i < 64; ++i) {
printf("Number: Count: \n");
}
}
Which will just print the following 64 times:
Number: Count:
Are you trying to print out the contents of your array foo[65]? If so that is also uninitialized so you'll need to insert integers first before you view them.
Initialize i, otherwise it could be any random number. Unlike some other languages, C does not automatically initialize variables to 0 (or the equivalent) unless they are global variables.
#include <stdio.h>
int main() {
int foo[65];
for(int i = 0; i < 64; ++i) {
printf("Number: Count: \n");
}
}
Related
I want to make a simple variable for number of the round for a loop, so I tried my code
int size,counter,marks[size];
scanf("enter %d/n",&size);
for(counter=0;counter<size;counter++)
{
scanf("%d",&marks[counter]);
}
and compiled with no error but in run, it just shows "process returned -1073741571 <0*c00000FD>.
so I tried gets function and it shows "too many arguments to function 'gets' ".
int size;
int counter;
int marks[size];
scanf("enter %d/n",&size);
for(counter=0;counter<size;counter++)
{
gets("%d",&marks[counter]);
}
I'm using code::blocks 17.12 and the gnu compiler.
size can have any value when the array marks is allocated because it is not initialized. The array might be smaller than the entered size and so marks are stored in non-allocated memory, giving you the error.
This is a possible solution, but it doesn't compile with strict ISO C90. Presumably your CodeBlocks uses GCC that accepts variable length arrays and mixed declarations and code.
#include <stdio.h>
int main(void) {
int size;
printf("enter size: ");
scanf("%d",&size);
int marks[size];
int counter;
for (counter = 0; counter < size; counter++) {
scanf("%d", &marks[counter]);
}
for (counter = 0; counter < size; counter++) {
printf("%d: %d\n", counter, marks[counter]);
}
return 0;
}
BTW, please don't say "build error" if you have a runtime error. ;-)
Please don't use gets. It's dangerous.
As for your error in the scanf example, the first problem is the line
int size,counter,marks[size];
which declares marks with the uninitialized size value. Try initializing size first, then declaring the marks array.
Your second problem is scanf formatting string. Use scanf to read formatted input, not output a prompt. Use puts or printf for that.
Here's a full example:
#include <stdio.h>
int main(void) {
int size;
printf("Enter a size value: ");
scanf("%d", &size);
int marks[size];
for (int i = 0; i < size; i++) {
printf("Enter element %d: ", i);
scanf("%d", &marks[i]);
}
printf("You entered: ");
for (int i = 0; i < size; i++) {
printf("%d ", marks[i]);
}
puts("");
return 0;
}
Here's a sample run:
Enter a size value: 4
Enter element 0: 88
Enter element 1: 77
Enter element 2: 66
Enter element 3: 55
You entered: 88 77 66 55
If you're writing ANSI C-compatible code you can use dynamic memory with malloc:
#include <stdio.h>
#include <stdlib.h>
int main(void) {
int i, size, *marks;
printf("Enter a size value: ");
scanf("%d", &size);
if (size < 1) {
fprintf(stderr, "Invalid size specified\n");
exit(1);
}
marks = malloc(size * sizeof(int));
if (!marks) {
fprintf(stderr, "malloc failed\n");
exit(1);
}
for (i = 0; i < size; i++) {
printf("Enter element %d: ", i);
scanf("%d", &marks[i]);
}
printf("You entered: ");
for (i = 0; i < size; i++) {
printf("%d ", marks[i]);
}
free(marks);
puts("");
return 0;
}
size must have a defined value, for example:
#include <stdio.h>
int main()
{
int size;
size = 5; // size must be constant
int counter, marks[size];
for (counter = 0; counter < size; counter++)
{
scanf("%d", &marks[counter]);
}
//Printing it returns correct values:
for (counter = 0; counter < size; counter++)
{
printf("%d\n", marks[counter]);
}
}
You can instead input it's value from the user if you want.
However, if for some reason, size is to be defined after the array is declared, use pointers:
#include <stdio.h>
#include "stdlib.h"
int main()
{
int size;
int counter, *marks;
size = 5; //declared after the array
marks = (int *)malloc(size * sizeof(int));
for (counter = 0; counter < size; counter++)
{
scanf("%d", &marks[counter]);
}
//Printing it returns correct values:
for (counter = 0; counter < size; counter++)
{
printf("%d\n", marks[counter]);
}
//Don't forget to free the array in the end
free(marks);
}
How to read space-separated integers representing the array's elements and sum them up in C?
I used the below code but it reads all the elements in a new line:
#include <math.h>
#include <stdio.h>
int main() {
int i = 0, N, sum = 0, ar[i];
scanf("%d" , &N);
for (i = 0; i < N; i++) {
scanf("%d", &ar[i]);
}
for (i = 0; i < N; i++) {
sum = sum + ar[i];
}
printf("%d\n", sum);
return 0;
}
Your array ar is defined with a size of 0: the code invokes undefined behavior if the user enters a non zero number for the number of items.
Furthermore, you should check the return value of scanf(): if the user enters something not recognized as a number, your program will invoke undefined behavior instead of failing gracefully.
Here is a corrected version:
#include <stdio.h>
int main(void) {
int i, N, sum;
if (scanf("%d", &N) != 1 || N <= 0) {
fprintf(stderr, "invalid number\n");
return 1;
}
int ar[N];
for (i = 0; i < N; i++) {
if (scanf("%d", &ar[i]) != 1) {
fprintf(stderr, "invalid or missing number for entry %d\n", i);
return 1;
}
}
sum = 0;
for (i = 0; i < N; i++) {
sum += ar[i];
}
printf("%d\n", sum);
return 0;
}
Note that the program will still fail for a sufficiently large value of N as there is no standard way to check if you are allocating too much data with automatic storage. It will invoke undefined behavior (aka stack overflow).
You should allocate the array with malloc() to avoid this:
#include <stdio.h>
#include <stdlib.h>
int main(void) {
int i, N, sum;
int *ar;
if (scanf("%d", &N) != 1 || N <= 0) {
fprintf(stderr, "invalid number\n");
return 1;
}
ar = malloc(sizeof(*ar) * N);
if (ar == NULL) {
fprintf(stderr, "cannot allocate array for %d items\n", N);
return 1;
}
for (i = 0; i < N; i++) {
if (scanf("%d", &ar[i]) != 1) {
fprintf(stderr, "invalid or missing number for entry %d\n", i);
return 1;
}
}
sum = 0;
for (i = 0; i < N; i++) {
sum += ar[i];
}
printf("%d\n", sum);
free(ar);
return 0;
}
Finally, there is still a possibility for undefined behavior if the sum of the numbers exceeds the range of type int. Very few programmers care to detect such errors, but it can be done this way:
#include <limits.h>
...
sum = 0;
for (i = 0; i < N; i++) {
if ((sum >= 0 && arr[i] > INT_MAX - sum)
|| (sum < 0 && arr[i] < INT_MIN - sum)) {
fprintf(stderr, "integer overflow for entry %d\n", i);
return 1;
}
sum += ar[i];
}
#include <math.h>
#include <stdio.h>
int main()
{
int i=0,N,sum=0;
scanf("%d" ,&N);
int ar[N];
for(i=0; i<N; i++)
scanf("%d",&ar[i]);
for(i=0; i<N; i++)
sum=sum+ar[i];
printf("%d\n", sum);
return 0;
}
This should be the code.
You have initially declared the array of size 0 (because i=0).
Even though you declared the array of size 0, when I ran it on my machine, it actually executed successfully with the correct output.
This is generally due to undefined behavior which means that we can only guess the output when the code is correct. If the code has undefined behavior, then it can do whatever it wants (and in the worst case the code will execute successfully giving the impression that it's actually correct).
Declaring a Variable Size Array (VLA) is optional in C11 standard. Thus, it depends on the implementation of the compiler whether it will support VLA or not. As pointed out by #DavidBowling in comments, if the compiler does support, then declaring a VLA of size 0 can invoke undefined behavior (which you should avoid in all cases). If it doesn't support, then this will simply give a compilation error and you'll have to declare the array size as some integer constant (example, int arr[100];).
#include <math.h>
#include <stdio.h>
int main()
{
int i=0,N,sum=0;
scanf("%d" ,&N);
int ar[N];
for(i=0; i<N; i++)
{
scanf("%d",&ar[i]);
}
for(i=0; i<N; i++)
{
sum=sum+ar[i];
}
printf("%d\n", sum);
return 0;
}
You should declare the array after accepting the value of N.
#include <math.h>
#include <stdio.h>
int main()
{
int i=0,N,sum=0;
scanf("%d" ,&N);
int ar[N];
for(i=0; i<N; i++)
{
scanf("%d",&ar[i]);
sum=sum+ar[i];
}
printf("%d\n", sum);
return 0;
}
As this is a very simple question I'll expand it a bit to include some good programming practices.
1. Analyze the problem
We have to complete two tasks here:
Read and store the numbers to array.
Sum the array elements.
Of course you can both read and calculate the same time, but we ❤ the SoC design principle. This will help you later with bigger programs.
2. Create the program structure
In this state we have to consider what function to use, as we already solved the data structure problem (we use array).
Of course, we always can put the whole procedure in main function but this would break the SoC principle.
The main principle here is:
I create a function for a separate procedure.
So we'll have to build two functions. Let's consider the following example:
ReadArrayData will be used to read the data from the standard input (your keyboard in other words) to array. But what will declare as parameters? We surely have to pass the array and the array size. The return type of this function will be void (we don't have to return something).
Keep in mind that if you pass array to function you can manipulate it as you please and keep these changes in your main program. This is because the arrays are passed always by reference to a function.
In the end this will be your function prototype:
void ReadArrayData(int arraySize, int array[]);
CalculateArraySum will be used to calculate the sum of the array elements. The function prototype will be the same as for ReadArrayData with the difference that the returning type will be int (we return the sum).
int CalculateArraySum(int arraySize, int array[]);
3. Write your program
#include <stdio.h>
void ReadArrayData(int arraySize, int array[]);
int CalculateArraySum(int arraySize, int array[]);
int main(void) {
int N;
printf("Give the array size: ");
scanf("%d", &N);
int array[N];
ReadArrayData(N, array);
int sumOfArrayElements = CalculateArraySum(N, array);
printf("The sum of array elements is %d.\n", sumOfArrayElements);
return 0;
}
void ReadArrayData(int arraySize, int array[]) {
printf("Give %d elements: ", arraySize);
for (int i = 0; i < arraySize; ++i) {
scanf("%d", &array[i]);
}
}
int CalculateArraySum(int arraySize, int array[]) {
int sum = 0;
for (int i = 0; i < arraySize; ++i) {
sum += array[i];
}
return sum;
}
I know this was a large scaled answer, but I saw you are new to computer programing. I just wanted to present you the main functionality to solve all kinds of problems. This was just a small introduction. In the end, you have to remember what steps we take to solve a problem. With time and as you solve many problems you will learn many many other things.
Sorry for that title. I really didn't know how to define this problem.
I was needed to declare integer array of N numbers and to fill it with random nums in void function. Then that array needs to be printed in main. The thing is that i am not allowed to use printf in void function so only way to print in main is to use pointers I guess. My knowledge is limited as I am beginner at pointers. Thx in advance and sorry for bad english.
Here is my code so far. When I compile it marks segmentation error.
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
void form();
int main()
{
int N, a[100];
printf("Input index: \n");
scanf("%d", &N);
form(N, &a);
printf("Array: \n");
for (int i = 0; i < N; i++) {
printf("a[%d] = %d", i, a[i]);
}
}
void form(int N, int *ptr[100])
{
srand(time(NULL));
for (int i = 0; i < N; i++) {
*ptr[i] = rand() % 46;
}
There are several issues in your code.
1) Your array decalaration form() is obsolete. Use proper prototype.
2) For declaring a VLA, declare it after reading N instead of using a fixed size array.
3) An array gets converted into a pointer to its first element when passed to a function. See: What is array decaying?
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
void form(int, int*); /* see (1) */
int main(void) /* Standard complaint prototype for main.
If you need to pass arguments you can use argc, and argv */
{
int N;
printf("Input size: \n");
scanf("%d", &N);
int a[N]; /* see (2) */
form(N, a); /* see (3) */
printf("Array: \n");
for (int i = 0; i < N; i++) {
printf("a[%d] = %d", i, a[i]);
}
}
void form(int N, int *ptr) { /* Modified to match the prototype
srand(time(NULL));
for (int i = 0; i < N; i++) {
ptr[i] = rand() % 46;
}
}
So a couple things:
void form();
As Olaf was alluding to, this declaration is incorrect - you are missing the applicable parameters. Instead, it should be
void form(int N, int ptr[100]);
The main reason your program is crashing is because of the following line:
*ptr[i] = rand() % 46;
You are dereferencing the pointer at i, which is actaully giving you a number - what you want is to assign the value of the pointer at i the new random value:
ptr[i] = rand() % 46;
As related reading, see this question about passing an array in as a function parameter (basically, int ptr[] is the same thing as int * ptr)
Small modifications on your code:
1) Correction and simplification of parameter handling at function call. Just hand over "a", it's an array, so it is an address, you can use int *ptr, or int ptr[], or int ptr[100] in the formal parameter list for it. So you can use simply ptr[i] in your function.
2) Make a prototype for function from old-style declaration providing parameter list.
3) int i; declaration before the for loop - not mandatory, depends on your compiler standard
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
void form(int N, int *ptr);
int main()
{
int N, a[100];
printf("Input index: \n");
scanf("%d", &N);
form(N, a);
printf("Array: \n");
int i;
for (i = 0; i < N; i++) {
printf("a[%d] = %d", i, a[i]);
}
}
void form(int N, int *ptr)
{
srand(time(NULL));
int i;
for (i = 0; i < N; i++) {
ptr[i] = rand() % 46;
}
}
#include "stdafx.h"
#include "stdio.h"
#include <string.h>
void main() {
int Results[8];
int i = 0;
int max = 0;
int maxindex;
printf("Enter the results of your 7 leavin cert subjects: ");
do {
printf("\nSubject %d: ", i + 1);
scanf_s("%d", Results);
i++;
} while (i < 7);
for (i < 7; Results[i] > 0; i++)
if (Results[i] > max)
max = Results[i];
printf("The best grade is %d", max);
}
Hello, so basically I'm trying to print out the largest number(Best result) by using a for loop. However it keeps telling me the that the best result is 0.
Does anybody know what I'm doing wrong. Any help would be greatly appreciated.
There are 2 major problems in your code:
You read all numbers into Results[0] with the scanf_s("%d", Results);. You should instead write:
if (scanf_s("%d", &Results[i]) != 1) {
/* not a number, handle the error */
}
The second loop is incorrect: for (i < 7; Results[i] > 0; i++) has multiple issues. Write instead for (i = 0; i < 7; i++)
And smaller ones too:
#include "stdio.h" should be written #include <stdio.h>
#include "stdafx.h" is not used, and so can be removed - regardless, it should be written as #include <stdafx.h> if it were to be used.
The Results array has size 8, but you only use 7 slots.
main should have prototype int main(void) or int main(int argc, char *argv[]) or equivalent.
favor idiomatic for (i = 0; i < 7; i++) loops over error prone do / while loops.
use braces for a non trivial loop body.
Here is a simpler and better version:
#include <stdio.h>
#include <string.h>
int main(void) {
int Results[7];
int i, n, max;
printf("Enter the results of your 7 leavin cert subjects: ");
for (i = 0; i < 7; i++) {
printf("\nSubject %d: ", i + 1);
if (scanf_s("%d", &Results[i]) != 1) {
printf("invalid number\n");
exit(1);
}
}
for (n = i, max = 0, i = 0; i < n; i++) {
if (Results[i] > max)
max = Results[i];
}
printf("The best grade is %d\n", max);
return 0;
}
I am attempting to write a program which examines values in two arrays of different sizes and adds the common elements into a third array.
I am using the following code:
#include <stdio.h>
int main(void) {
// your code goes here
int A[5], B[8], i, j, s=1;
int* c;
c=(int*)malloc(s*sizeof(int));
for(i=0;i<5;i++)
{scanf("\t %d", &A[i]);}
printf("\n");
for(j=0;j=8;j++)
{scanf("\t %d", &B[j]);}
for(i=0, j=0;i<5,j<8;i++,j++)
{
if(A[i]==B[j])
{
c[i]=A[i];
s++;
printf("\n %d", c[i]);
c=realloc(c, s*sizeof(int));
break;
}
}
return 0;
}
but when I try to execute it, it is giving the problem that the time limit has been exceed. What is causing this problem? For compilation I am using the on-line compiler ideone.
Below is the code that would work.
Except for the mentioned problems in the for loops, assignment to array c was wrong.
#include <stdlib.h>
#include <stdio.h>
int main(void) {
int A[5], B[8], i, j, s=1;
int* c;
c=(int*)malloc(s*sizeof(int));
for(i=0;i<5;i++) {scanf("\t %d", &A[i]);}
printf("\n");
for(j=0;j<8;j++) {scanf("\t %d", &B[j]);}
for(i=0;i<5;i++){
for(j=0;j<8;j++){
if(A[i]==B[j]){
c[s-1] = A[i]; // use s-1 as an index
printf("\n %d", c[s-1]);
s++;
c=(int*)realloc(c, s*sizeof(int));
}
}
}
return 0;
}
Hmmm...where to begin?
Are you only looking for characters that are the same AND in the same position? It LOOKS as though that is what you are trying to do, but as the array A and B have different dimensions, you are going to get into some trouble. And are you ONLY looking for the FIRST match? With the "break", you will stop after the first match.
Assuming you are looking for ALL element common to both lists -- in ANY position -- you will want code more like the following:
#include <stdio.h>
int main(void)
{
int A[5], B[8], C[8];
for (int i = 0; i < 5; i++)
scanf(" %d ", &A[i]);
printf("\n");
for (int i = 0; i < 8; i++)
scanf(" %d ", &B[i]);
int ci = 0;
for (int ai = 0; ai < 5; ai++)
{
for (int bi = 0; bi < 8; bi++)
{
if (A[ai] == B[bi])
{
C[ci] = A[ai];
ci++;
break;
}
}
}
C[ci] = 0;
printf("Common chars: %s\n", C);
return 0;
}
The key to what you want, I think, is the nested for loops, which iterate through EACH of the strings (A and B) separately, while looking for matching characters.