#include <stdio.h>
 
template <size_t N>
struct StrN
{
    char str[N];
 
    static void Swap(char *p0, char *p1)
    {
        StrN &s0 = *(StrN *)p0;
        StrN &s1 = *(StrN *)p1;
        StrN tmp = s0;
        s0 = s1;
        s1 = tmp;
    }
};
 
 
#define SWAP10(STR, IDX0, IDX1) StrN<10>::Swap(&STR[IDX0 * 10], &STR[IDX1 * 10])
 
 
int main()
{
 
    char str[21] = {"abcdefghijABCDEFGHIJ"};
 
    printf("Before swapping :\n%s\n\n", str);
 
    SWAP10(str, 0, 1);
 
    printf("After swapping :\n%s\n\n", str);
 
    return 0;
}

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