C-language pointer-based pointer exchange between two numbers (Code instances) and pointer instances

C-language pointer-based pointer exchange between two numbers (Code instances) and pointer instances

Exchange two numbers with pointers:

Void swap (int * p, int * q) {int temp; temp = * p; * p = * q; * q = temp;} int main () {int a = 3, * p, c = 5, * q; p = & a; // assign the address of variable a to pointer p, that is, p points to aq = & c; swap (p, q); printf ("a = % d, c = % d \ n", a, c); return 0 ;}

Note: In a sub-method, two numbers can only be passed by reference. Because java is passed by value, and c can pass a pointer, c can modify the value of a temporary variable.

Java cannot modify the value of a temporary variable. java obtains the running result of the method through the return value:

Public static void main (String [] args) {int a = 3, B = 5; fun (a, B); System. out. println ("a =" + a + "; B =" + B);} private static void fun (int p, int q) {p * = 2; q * = 2 ;}

C can directly modify the value of the Temporary Variable through the pointer:

Void fun (int * p, int * q) {* p * = 2; * q * = 2;} int main () {int a = 3, * p, c = 5, * q; p = & a; // assign the address of variable a to the pointer p, that is, p points to aq = & c; fun (p, q ); printf ("a = % d, c = % d \ n", a, c); return 0 ;}