How can i run a command only one time inside of for loop?

Question

How can i run a command only one time inside of for loop?
I couldn't find how to do it so i wrote code like that. But the problem on this code you can see when the program goes to else command it doesn't work.

I just wanted to see odd and even numbers with using for loop but I don't want to get result like;

Even numbers :12
Even numbers :28
Even numbers :46

I just want to see only one time print Even numbers and then print numbers like;

Even numbers: 
12
28
46

etc.

I hope I could explain clearly.

My alternative but wrong code is:

#include <stdio.h>

int main()
{   
    int num [] = {12, 14, 16, 33, 65, 98, 45, 25, 87, 18, 20};
    
    printf("even numbers:");
    printf("\t\t\t\t Odd numbers:");

    for (int i = 0; i < 11; i++) {
        if (num[i] % 2 == 0) {
            printf("\n%d", num[i]);
        }
        else {
            printf("\t\t\n%d");
        }   
    }
        
    return 0;
}

Answer 1

You want two loops:

#include <stdio.h>

int main(void)
{
    int num[] = {12,14,16,33,65,98,45,25,87,18,20};
    size_t n = sizeof num / sizeof *num;

    printf ("Even numbers:\t\t\t\tOdd numbers:\n");

    for (size_t i = 0; i < n; i++) {
        if (num[i] % 2 == 0) {
            printf ("%d ", num[i]);
        }
    }
    printf("\r\t\t\t\t\t");
    for (size_t i = 0; i < n; i++) {
        if (num[i] % 2 != 0) {
            printf ("%d ", num[i]);
        }
    }
    printf("\n");
    return 0;
}

Output:

Even numbers:               Odd numbers:
12 14 16 98 18 20           33 65 45 25 87 

Notice the \r to go to the beginning of the line

Answer 2

Here a different format:

#include <stdio.h>

int main(void) {
    unsigned num []={12,14,16,33,65,98,45,25,87,18,20};
    printf("even numbers"
        "\todd numbers\n");
    const char *prefix[] = {"", "\t\t"};
    for(unsigned i = 0; i < sizeof(num) / sizeof(*num); i++) {
        printf("%s%u\n", prefix[num[i] % 2], num[i]);
    }
}

and the output is:

even numbers    odd numbers
12
14
16
                33
                65
98
                45
                25
                87
18
20

Answer 3

EDIT: OP has been edited to show desired output. I had add '\n' to two lines of this to effect the change.

"Factoring out" common processing into a function is always a good idea.

#include <stdio.h>

void show( int num[], int nItems, char *title, int rem ) {
    printf( "%s\n", title );
    for( int i = 0; i < nItems; i++ )
        if( num[i]%2 == rem )
            printf( "%d\n", num[ i ] );
    printf( "\n" );
}

int main () {
    int num [] = { 12, 14, 16, 33, 65, 98, 45, 25, 87, 18, 20 };

    show( num, sizeof num/sizeof num[0], "even numbers: ", 0 );
    show( num, sizeof num/sizeof num[0], "odd numbers: ", 1 );

    return 0;
}

Output:

even numbers:
12
14
16
98
18
20

odd numbers:
33
65
45
25
87

Answer 4

Based on the assumption that the least changes to your shown code, with explanation, are most helpful, here is my explained solution:

#include <stdio.h>

int main()
{   
    int num [] = {12, 14, 16, 33, 65, 98, 45, 25, 87, 18, 20};
    
    printf("even numbers:");
    printf("\tOdd numbers:\n"); // newline after the output, one tab, no blanks

    for (int i = 0; i < 11; i++) {
        if (num[i] % 2 == 0) {
            printf("%d\n", num[i]); // newline after output
        }
        else {
            printf("\t\t%d\n", num[i]); // tabs, then output, then newline
        }   
    }
        
    return 0;
}

this gets you an output of:

even numbers:   Odd numbers:
12
14
16
                33
                65
98
                45
                25
                87
18
20

Your problem was only caused by missapplied whitespaces.
(Apart from accidentally dropping the parameter for the odd output....)
Doing newlines after output is a good practice, but that is a matter of taste.
Important is to not output tabulators followed by a newline; because the newline spoils the effect of the tabulators.

Here is the version with newlines before output (for really minimal changes), but I recommend against it.

#include <stdio.h>

int main()
{   
    int num [] = {12, 14, 16, 33, 65, 98, 45, 25, 87, 18, 20};
    
    printf("even numbers:");
    printf("\t\t\t\t Odd numbers:");

    for (int i = 0; i < 11; i++) {
        if (num[i] % 2 == 0) {
            printf("\n%d", num[i]);
        }
        else {
            printf("\n\t\t\t\t\t %d", num[i]); // newline, tabs, blank, output
        }   
    }
        
    return 0;
}

This gets you an output of:

even numbers:                            Odd numbers:
12
14
16
                                         33
                                         65
98
                                         45
                                         25
                                         87
18
20

Wider, because I left the multiple tabulators and the unneeded blank in.