A C Programming Language Puzzle

Give a = 12 and b = 36 write a C function/macro that returns 3612 without using arithmetic, strings and predefined functions.

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Below is one solution that uses String Token-Pasting Operator (##) of C macros. For example, the expression “a##b” prints concatenation of ‘a’ and ‘b’.

Below is a working C code.

#include <stdio.h>
#define merge(a, b) b##a
int main(void)
{
    printf("%d ", merge(12, 36));
    return 0;
}

Output:

3612

Thanks to an anonymous user to suggest this solution.