例8-3指针作为函数参数模拟角色互换调用哪个函数，可以交换main（)int main (void)inta= 1, b = 2;中变量a和b的值？int*pa=&a,*pb=&b;void swap1(int x, int y),swap2(int *px, int*py ),swap3 (int *px, int*py);swap1 (a, b);printf ("After calling swap1:a=%d b=%din",a, b);a=1; b=2;swap2(pa,pb);printf("After callingswap2: a=%d b=%din",a, b);a=1; b=2;swap3(pa,pb);printf("Aftercallingswap3:a=%db=%dln",a, b);return O;1例8-3 指针作为函数参数模拟角色互换 int main (void) { int a = 1, b = 2; int *pa = &a, *pb = &b; void swap1(int x, int y), swap2( int *px, int *py ), swap3 (int *px, int *py); swap1 (a, b); printf (“After calling swap1: a=%d b=%d\n”, a, b); a = 1; b = 2; swap2(pa, pb); printf (“After calling swap2: a=%d b=%d\n”, a, b); a = 1; b = 2; swap3(pa, pb); printf (“After calling swap3: a=%d b=%d\n”, a, b); return 0; } 调用哪个函数，可以交换main () 中变量a和b的值?