For some reason that I can't comprehend ,this program keeps looping when I execute it in the CMD.
#include <stdio.h>
int main() {
char array [] = {'b','f','r','o','a','u','v','t','o','\0'};
int grootteArray = sizeof(array);
int grootteChar = sizeof(char);
int lengteArray = grootteArray / grootteChar;
int i;
for (i = 0; i < lengteArray + 1; i + 2) {
printf("%c", array[i]);
}
return 0;
}
Your counter variable remains the same after each loop. You need to increase it by assigning the new value:
for (i=0; i<lengteArray+1; i=i+2) //change to this
Because i never changes. You should assign i + 2 to i:
for (i=0; i<lengteArray+1; i = i + 2) {
↑
The way you wrote it has no effect on the value of i, it just calculates i + 2 and does nothing with this value.
You're getting infinite loop because i is set to 0 and it's always 0.. So once i < legteArray + 1, it'll remain like that.
The value of i is never changed.
try this:-
for (i=0; i<lengteArray+1; i = i+2) {
i is not modifying in you loop. Also i < lengteArray + 1 will lead you to print garbage value and undefined behavior.
for (i = 0; i < lengteArray; i++){
printf("%c", array[i]);
}
If you are interested in incrementing i by 2 in each iteration then you can use i += 2
for (i = 0; i < lengteArray; i += 2){
printf("%c", array[i]);
}
Related
i have the belowo loop in c that print the prime number
for(int i = 2; i<=arraySize; i++)
{
//If arraySize is not 0 then it is prime
if (numbers[i]!=0)
printf("%d,",numbers[i]);
}
the out put after enter 50 for example is
2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,
i want to to not print the last comma how i can do it
i tried this code but not working
printf("%d%s", numbers[i], (i !=arraySize-1) ? "," : "");
Instead of printing a comma after each number, print it before. Then you can use a variable to tell if this is the first number being printed, and not print the comma.
first=true;
for(int i = 2; i<=arraySize; i++)
{
//If numbers[i] is not 0 then it is prime
if (numbers[i]!=0) {
printf("%s%d", (first ? "" : ","), numbers[i]);
first = false;
}
}
I like both the other answers but just want to throw in this error prone variant on the same theme.
_Bool first = true;
for (int i = 2; i <= arraySize; i++) {
if (numbers[i] != 0) {
printf(",%d" + first, numbers[i]);
first = false;
}
}
If first is true the actual formatting string will become "%d". If it's false it'll become ",%d".
Simple: Use a pointer to the "prefix" string, printed AHEAD of the next value:
char *sep = "";
for(int i = 2; i <= arraySize; i++ ) {
if( numbers[i] ) {
printf( "%s%d", sep, numbers[i] );
sep = ", "; // I added a SP, too
}
}
Here's an alternative that uses a "limited scope" variable to index a static string. For clarity in this example, the array boundaries have been adjusted.
int main( void ) {
int numbers[] = { 1, 1, 4, 8, 9, 0, 7 };
int arraySize = sizeof numbers/sizeof numbers[0];
for( int i = 0, out = 0; i < arraySize; i++ )
if( numbers[i] )
printf("%s%d", &","[!out++], numbers[i] );
return 0;
}
The negated boolean post-incrementing value of out provides the address of the '\0' to the first instance, then the address of "," in subsequent instances.
1,1,4,8,9,7
The answers already here are fine, but I'd like to add a "simpler" solution. Simpler in that it doesn't require any further logic or extra variables. It does, however, require that you know that the first number is non-zero.
printf("%d", numbers[2]);
for (int i = 3; i < arraySize; i++)
{
if (numbers[i] != 0)
printf(",%d", numbers[i]);
}
I think the other answers overcomplicates things. I don't see any reason to have a test for every iteration in the loop. Instead, I'd simply do the special case first:
printf("%d", numbers[2]);
for (int i = 3; i <= arraySize; i++) {
if (numbers[i]!=0)
printf(",%d", numbers[i]);
}
This will however need some additional code to correctly handle the case where arraySize is lower than 3.
But I would choose another approach from the beginning, and that is writing a good function for printing an array. Could look like this:
void printArray(const int *array, int size) {
putchar('['); // Of course this is optional
if(size > 0) {
printf("%d", array[0]);
for(int i=1; i<size; i++)
printf(",%d", array[i]);
}
putchar(']'); // And this too
}
and then something like this:
int convertArray(const int *numbers, int *array, int size) {
int ret = 0;
for(int i=0; i<size; i++) {
if(number[i] != 0) {
array[ret] = numbers[i];
ret++;
}
}
return ret;
}
So here is the problem: Write a program that accept an integer n, print out the largest number but smaller or equal n that is the product of two consecutive even number. Example: Input: 12, Output: 8 ( 2x4 )
Here is my code :
#include <stdio.h>
int main()
{
int n;
scanf("%d", &n);
for (int i = n; i >= 0; i--)
{
for (int j = 0; j <= n; j = j + 2)
{
if ( i == j * (j+2) )
{
printf("%d ", i);
break;
}
}
}
return 0;
}
So if i input 20, it will print out 8 and 0 instead of 8, if i input 30, it will print out 24,8 and 0 instead of just 24. How do i make it stop after printing out the first number that appropriate ?
You need to stop an outer loop from processing, for example by using a boolean flag (meaning "solution found, we finish work") or a goto statement.
#include <stdio.h>
int main() {
int n;
scanf("%d", &n);
int solutionFound = 0;
for (int i = n; i >= 0; i--) {
// this could also be put into for's condition i.e. "i >= 0 && !solutionFound"
if (solutionFound) {
break;
}
for (int j = 0; j <= n; j = j + 2) {
if ( i == j * (j+2) ) {
printf("%d ", i);
solutionFound = 1;
break;
}
}
}
return 0;
}
EDIT: immediate return as noted in the comments is also a nice idea, if you don't need to do anything later.
Your problem is that you are nested - in a for loop which is inside another for loop - when you want to stop processing.
Some languages would let you code break 2; to indicate that you want to break out of 2 loops. Alas, C i snot such a language.
I would recommend that you code a function. That would serve a few porpoises: 1) your main should be "lean & mean" 2) as your programs get larger, you will learn the benefits of putting individual coding tasks into functions 3) you can use return; instead of break; and it will exit the function immediately.
Something like this:
#include <stdio.h>
void FindNeighbouringDivisors(int n)
{
for (int i = n; i >= 0; i--)
{
for (int j = 0; j <= n; j = j + 2)
{
if ( i == j * (j+2) )
{
printf("%d times %d = %d", j, j + 2, i);
return;
}
}
}
printf("There are no two adjacent even numbers which can be multiplied to give %d", n);
}
int main()
{
int n;
scanf("%d", &n); /* could get from comamnd line */
FindNeighbouringDivisors(n);
return 0; /* should be EXIT_SUCCESS */
}
Btw, when you have a problem with your code, ask a question here. When you have it working, consider posting it at our code review site where more experienced programmers can give you advice on how to improve it. It's a great way to learn
Break only breaks you out of immediate loop, so either use flags or just use return to terminate the execution. Or you can even use following code:
#include <stdio.h>
int main()
{
int n;
scanf("%d", &n);
for (int j = 0; j <= n; j = j + 2)
{
if ( n < j * (j+2) )
{
printf("%d ", j*(j-2));
break;
}
}
return 0;
}
So, I'll preface this by saying I'm fairly new to pointers and dynamic allocation. Currently I am trying to store a file that contains a 3x3 matrix of ints into a 2d array. I've tried debugging my code and what I notice is that it reads my first 2 values, but than begins to generate random garbage into my 2d array. I assume that I am storing my ints incorrectly and there is a flaw in my logic, but as I keep trying to think about it, I can't seem to find where it could be incorrect as they are moving from [0][0], [0][1], etc.
Here is my code for reference. Thanks, I'd appreciate just some guidance on how I can troubleshoot this problem for this specific case and future issues.
#include <stdio.h>
#include <stdlib.h>
int main() {
FILE* fpM1;
fpM1 = fopen("m1.txt", "r");
int i, j, row1 = 2, col1 = 2;
int* ptrM1 = (int* )malloc(9 * sizeof(int));
if (fpM1 != NULL) {
for (i = 0; i < row1; i++) {
for (j = 0; j < col1; j++) {
fscanf(fpM1, "%d", ((ptrM1 + i) + j));
}
}
for (i = 0; i < row1; i++)
for (j = 0; j < col1; j++) {
{
printf(" %d", *((ptrM1 + i) + j));
}
}
}
free(ptrM1);
fclose(fpM1);
return 0;
}
Your for loops end too fast. You should use <= instead of <. After that, everything seems to work perfectly.
Maybe you should consider adding new line in outer for loop during printing array. It will help with clarity:
for (i = 0; i < row1; i++) {
for (j = 0; j < col1; j++) {
printf(" %d", *(ptrM1 + i));
}
printf("\n");
}
Also you don't need those double brackets before first printf statement. In C you can put many scopes without context, but you shouldn't do that without reason.
EDIT: It actually doesn't work. Reading from file should be done this way:
fscanf(fpM1, "%d", ptrM1 + (i * (col1 + 1) + j));
and printing:
printf(" %d", ptrM1[i * (col1 + 1) + j]);
I have an array with 100 numbers in it, and I am trying to print it out with only 10 ints on each line, and a tab between each number. It is only printing the first 10 integers and then stopping, which makes sense because of my for loop. I am clearly missing part of it to allow for it to continue through the array. I was going to try to add the line
for(int line_num = 0; line_num < 10; line_num+=10)
before the for statement after the while loop
int array_value;
int length_of_array = 100;
while (length_of_array <= 100){
for(array_value = 0; array_value < 10; ++array_value){
printf("%d ", A[array_value]);
++length_of_array;
}
I was also thinking of including a line like
if (array_value % 10 == 0)
printf("\n");
I figured it out! Posted the answer below.
This might be what you're looking for:
/* test.c */
#include <stdio.h>
#define ELEMENTS 100
int main (void)
{
int array [ELEMENTS];
for ( int i = 0; i < ELEMENTS; ++i )
array [i] = i;
for ( int i = 0; i < ELEMENTS; ++i ) {
printf ("%i", array[i]);
if ( (i + 1) % 10 != 0 )
printf ("\t");
else
printf ("\n");
}
return 0;
}
edit: Because of the way the tab can extend to the next line at the end of the line you have to be careful with the tab and new line character.
For clarity, rename length_of_array to offset_in_array and then set it to zero at the start. I renamed array_value and corrected your length check. I also added a check to the inner loop in case the array length gets changed and doesn't divide by 10.
Something like:
int i;
#define ARRAY_LENGTH 100
int offset_in_array = 0;
while (offset_in_array < ARRAY_LENGTH){
for(i = 0; i < 10 && offset_in_array < ARRAY_LENGTH; ++i){
printf("%d ", A[offset_in_array]);
++offset_in_array;
}
}
I haven't tried running this but it should be closer.
Just print a newline every tenth number... If it's not a tenth number, then print a tab.
for (size_t i = 0; i < array_length; ++i) {
printf("%d%c", A[i], i % 10 != 9 ? '\t' : '\n');
}
Live code available at onlinedbg.
Just change the value of length_of_array to 0 and print \n after a for loop.
int array_value;
int length_of_array = 0;
while (length_of_array <= 100) {
for(array_value = 0; array_value < 10; ++array_value){
printf("%d ", A[array_value]);
++length_of_array;
}
printf("\n");
}
You can use the following solution to print 10 lines of 100 array values in C:
for (int i = 0; i < 100; ++i){
printf("%i\t", A[i]);
if ((i+1)%10 == 0){
printf("\n");
}
}
This is a program on sorting integers.
#include <stdio.h>
int main(void) {
int n, i, j, k;
int nmbr[100];
printf("\n How many numbers ? ");
scanf("%d", &n);
printf("\n");
for (i = 0; i < n; ++i) {
printf(" Number %d : ", i + 1);
scanf("%d", &nmbr[i]);
}
for (i = 0; i < n; ++i) {
for (j = 0; j < n; ++j) {
if (nmbr[j] > nmbr[j + 1]) {
k = nmbr[j];
nmbr[j] = nmbr[j + 1];
nmbr[j + 1] = k;
}
}
}
printf("\n Numbers after sorting : \n");
for (i = 0; i < n; ++i) {
printf (" %d", nmbr[i]);
}
return 0;
}
It works fine, but when I enter some number that contains more than 2 digits, the first number that is printed is negative and really big. I don't also get the last integer too. I enter N as 4, then the numbers I entered were 25, 762, 588, and 34. The result I get is:
-1217260830 25 34 588
What seems to be the problem?
You are running the loop as for (j = 0; j < n; ++j) which means j will have values from 0 to n-1 which are valid array indices (or array elements with relevant values).
But, inside that loop you are accessing an element beyond the last. For instance, in
if (nmbr[j] > nmbr[j + 1])
you are accessing nmbr[j + 1]. If the current value of j in n-1, then you are accessing nmbr[n-1 + 1] i.e. nmbr[n] which will be a value outside the array and may contain a garbage value (which might as well be negative!).
If you are trying something like Bubblesort, you might want to run the inner loop like for (j = 0; j < n - 1; ++j).
There are multiple problems in your code:
You do not check the return values of scanf(). If any of these input operations fail, the destination values remain uninitialized, invoking undefined behavior and potentially producing garbage output.
You do not verify that the number of values provided by the user is at most 100. The reading loop will cause a buffer overflow if n is too large.
Your sorting logic is flawed: in the nested loop, you refer to nmbr[j + 1] which is beyond the values read from the user. This invokes undefined behavior: potentially causing a garbage value to appear in the output.
Here is a corrected version:
#include <stdio.h>
int main(void) {
int n, i, j, k;
int nmbr[100];
printf("\n How many numbers ? ");
if (scanf("%d", &n) != 1 || n > 100) {
printf("input error\n");
return 1;
}
printf("\n");
for (i = 0; i < n; ++i) {
printf(" Number %d : ", i + 1);
if (scanf("%d", &nmbr[i]) != 1) {{
printf("input error\n");
return 1;
}
}
for (i = 0; i < n; ++i) {
for (j = 0; j < n - 1; ++j) {
if (nmbr[j] > nmbr[j + 1]) {
k = nmbr[j];
nmbr[j] = nmbr[j + 1];
nmbr[j + 1] = k;
}
}
}
printf("\n Numbers after sorting :\n");
for (i = 0; i < n; ++i) {
printf (" %d", nmbr[i]);
}
printf("\n");
return 0;
}
Your Sorting Logic is wrong. It should be:
for (i = 0; i < n; ++i){
for (j = 0; j < (n-1); ++j){
if (nmbr[j] > nmbr[j + 1]){
k = nmbr[j];
nmbr[j] = nmbr[j + 1];
nmbr[j + 1] = k;
}
}
You are trying to access out of bounds of array, when you iterate in your second loop using j. This is causing the garbage value.
As per your example involving 4 elements, when you try to access j+1, it will try to access nmbr[3+1] in the last iteration of second loop which leads to out of bounds access.
Problem is with the sorting logic as suggested by fellow coders. But It is always good coding habit to initialize the variables. Also use the qualifier if are dealing with positive numbers only.
unsigned int n = 0 , i = 0, j = 0, k = 0;
unsigned int nmbr[100] = {0};
If you would have initialized them, out put of your program would be following, which might help you tracing the problem by yourself.
0 25 34 588