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Story: I tried to convert a c99 script to regular gcc.
Problem: The output is empty.
Expected output: 3,2,1
length is the number of elements in the array.
Update: the script is designed to sort the elements of the array in a descending order.
The code:
#include <stdio.h>
int main() {
int arr[] = { 1,2,3 };
int temp = 0;
int length = sizeof(arr) / sizeof(arr[0]);
int i = 0;
int j = i + 1;
for (i < length; i++;) {
for (j < length; j++;) {
if (arr[i] < arr[j]) {
temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
}
int y = 0;
for (y < length; y++;) {
printf("%d ", arr[y]);
}
return 0;
}
Your syntax for for loops is the issue.
Here is the correct way to write your loops.
int i, j;
for (i = 0; i < length; ++i) // for (initialisation; test condition; operation)
{
for (j = i + 1; j < length; ++j) // note that j is initialized with i + 1 on each iteration of
// the outer loop. That's what makes the bubble sort work.
{
/* test and swap if needed */
}
}
for (i = 0; i < length; ++i) // note that i is reset to zero, so we can scan the array from
// a known position (the top) to bottom.
{
/* printout */
}
Your semicolon is in the wrong place, move it to the far left just inside the parentheses.
Loop syntax is:
for (intializer; break condition; iterator)
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This code is an exercise from a daily programming mailing list. I am trying to print out a list of given words in reverse order. The words are delimited by spaces. When running the code below, it enters into an infinite loop just printing the (new) first word. I have looked through the conditions and everything looks OK to me. I think it may take a fresh set of eyes to point out a simple mistake, but I can't find anything. Thanks to anyone who can lend a hand.
*Note: I am planning on adding back in the spaces to the output after this is figured out. I am aware the output will just be one long string without spaces so far.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main (void)
{
char *words;
words = "here world hello spam foo bar baz";
int space_indices[10];
int counter = 0;
// Find the spaces and keep track of the index numbers in the space_indices array
for (int i = 0; i < strlen(words); i++) {
if (words[i] == ' ') {
space_indices[counter] = i;
counter++;
}
}
for (int i = counter - 1; i >= 0; i--) {
if ( i = counter - 1) {
// Print the first word
for (int j = space_indices[i] + 1; j < strlen(words); j++) {
printf("%c", words[j]);
}
} else if (i >= 0) {
// Print the other words except for the last
for (int j = space_indices[i] + 1; j < space_indices[i + 1]; j++) {
printf("%c", words[j]);
}
} else {
// Print the last word
for (int j = 0; j < space_indices[0]; j++) {
printf("%c", words[j]);
}
}
}
}
As Havenard explained, the problem was that I was not using a comparison operation, I was using an assignment operator.
This:
if ( i = counter - 1)
should be:
if ( i == counter - 1)
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I have tried to write a sorting function sort(int *buffer, int array[], int size) which works in a way similar to the insertion sort - it takes the first element from the array, sets it as the first element of the buffer and then checks whether or not the next value showing up in the array is greater than the last value stored in the buffer. If yes, it keeps swapping the two elements until everything is in its place. This is my minimal working example:
#include <stdio.h>
void sort(int *buffer, int array[], int size) {
for(int i = 0; i < size; i++) {
buffer[i] = array[i];
while(i >= 1 && buffer[i] < buffer[i-1]) {
int tmp = buffer[i-1];
buffer[i-1] = buffer[i];
buffer[i] = tmp;
printf("i = %d i: %d, i -1 : %d \n",i, buffer[i], buffer[i-1]);
i--;
}
}
}
int main(void) {
int array[3] = {4,3,2};
int buffer[3];
sort(buffer, array, 3);
for(int i = 0; i < 3; i++) {
printf("%d", buffer[i]);
}
}
However, the output of this program is 222
To be honest, I don't see how it's even possible that three identical elements got placed in the buffer.
What can have gone wrong?
You are using the same variable for the inner while cycle and for the outer for loop. Use a different variable and copy the value of i to it in each iteration of the for.
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I try to do a function in order to sort an array and display after that only the prime number. But all the elements of my array are random numbers, and the problem is that the function display only negative prime numbers and not positive like 7 and 3, what can I do in order to solve the problem
int prime_arr(int size, int *arr, int *sort_arr)
{
int i, j, k = 0, flag;
for (i = 0; i < size; i++)
{
flag = 0;
for (j = 2; j < arr[i]/2; j++)
{
if (arr[i] % j == 0){
flag = 1;
break;
}
}
if (flag == 0){
sort_arr[k++] = arr[i];
}
}
return j;
}
I see 3 problems with the code:
1. You should return k, not j. k is the size of sort_arr
2. You should loop until arr[i] / 2, not one less than that (see <= in code below)
3. You do not handle negative numbers. Change your loop to the following:
for (j = 2; j <= abs(arr[i])/2; j++)
Without the code that prints your values, I'm not sure exactly what you're looking for, but hopefully fixing these will fix your problem.
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I am really struggling with learning programming via C. I seem to get the gist of things while going through the book's exercises but the second I try to implement something different it falls apart especially in regard to arrays.
I am making a simple game with a 2D character array. It should be 11x11. I am trying to write a function to set each index of the array as a blank space ' ' to start. My code compiles then I get a 'core dump' when I run it. Here is the code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
/*-------- GLOBAL FUNCTIONS --------*/
// Clear the Screen
void clear()
{
system("clear"); // For Linux/iOS
}
//---------- Creat Array(Game Board)
#define MAX 11 // Max number of characters in each row and column of array
char GameBoard[MAX][MAX];
// Clear Each Space in Array with Empty ("") Space
void ClearBoard(char GB[MAX][MAX])
{
for (int i = 0; i < MAX; ++i)
{
GameBoard[i][i] = ' ';
for (int j = 0; j < MAX; ++i)
{
GameBoard[i][j] = ' ';
}
}
}
int main()
{
ClearBoard(GameBoard);
return 0;
}
Any help towards understanding this better would be greatly appreciated, thank you.
your inner loop increments i until it is out of the array bounds
it should be ++j and not ++i
after MAX+1 iterations of the inner loop you're trying to access memory which is not allocated and that is why you get your error.
also the line GameBoard[i][i] = ' '; is unnecessary since it is taken care of in the inner loop when j == i
You need to change this line
for (int j = 0; j < MAX; ++i)
to
for (int j = 0; j < MAX; ++j)
Replace ++i with ++j in the line
for (int j = 0; j < MAX; ++i)
GameBoard[i][i] = ' ';
This line doesn't make any sense. Remove it.
for (int j = 0; j < MAX; ++i)
Should be j++.
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Assume the character a,b,c,d,e represent the number 1 to 9, and they cannot be equal to
each other.
Question:
How many equals that can meet (ab * cde = adb * ce).
Example:
36 * 495 = 396 * 45.
Here is my code,and the result is right.However,i think my code is too awkward,especially in (if(a!=b&&a!=c&&a!=d&&a!=e&&b!=c&&b!=d&&b!=e&&c!=d&&c!=e&&d!=e&&c*d*e!=0))
I would appreciate it if someone could give me a better solution.
#include<stdio.h>
main(){
int a,b,c,d,e,m,n,i=0;
long f1,f2,f3,f4;
for(m=11;m<=99;m++){
a=m/10;
b=m%10;
if(a!=b&&a*b!=0)
{
for(n=101;n<=999;n++)
{
c=n/100;
d=n%100/10;
e=n%10;
if(a!=b&&a!=c&&a!=d&&a!=e&&b!=c&&b!=d&&b!=e&&c!=d&&c!=e&&d!=e&&c*d*e!=0)
{
f1=a*10+b;
f2=c*100+d*10+e;
f3=a*100+d*10+b;
f4=c*10+e;
if(f1*f2==f3*f4) i++;
printf("\n%d%d*%d%d%d*=%d%d%d*%d%d\n",a,b,c,d,e,a,d,b,c,e);
}
}
}
}
printf("%d\n",i);
return 0;
}
If you can, instead of
int a,b,c,d,e;
Try to use
int numbers[5];
And then to check if your numbers are all different, you can use for loops
doubleOccurence = FALSE; /* where FALSE = 0 */
for (i=0; i < 4; i++) {
for (j=i+1; j < 5; j++) {
doubleOccurence = doubleOccurence || (numbers[i] == numbers[j]);
}
}
It looks a bit clearer to me.
Unfortunately you can't really iterate through a list of variables you are better off with an array of numbers like Julien mentions in his answer.
int nums[5];
replace a with nums[0], b with nums[1], etc....
But then I would go one step further to tidying up your code and call a function that takes in the array to check uniqueness:
if(listIsUnique(nums, 5)) // yes hardcoded the 5, but that can be sorted
{
...
}
And then:
bool listIsUnique(int* nums, int len)
{
for (int i = 0; i < len; i++)
for (int j = i + 1; j < len; j++)
if (nums[i] == nums[j])
return false; // return false as soon as you find a match - slightly faster :)
return true; // if we get here its a unique list :)
}
Note: code is untested, there may be mistakes :o