有两个字符串数组，即 string1 与 string2，不使用任何C/C++库函数的情况下，请问如何交换这两个字符串数组中的数据

void swapString(char *string1, char *string2, int len)
{
if ( 0 == string1 || 0 == string2 )
{
return;
}

for ( int i = 0; i < len; ++ i )
{
char tempChar = string1[i];
string1[i] = string2[i];
string2[i] = tempChar;
}
}

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);

char string1[20] = {"nihaoma"};
char string2[20] = {"haode"};
swapString((char *)&string1, (char *)&string2, 20);
qDebug() << "hanrong xx string" << string1 << string2;

return a.exec();
}