_21_교재 => 수업027_포인터와함수 , _21_문제 => 문제027_포인터와함수~문제027_포인터와함수04

• _21_교재

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• 수업027_포인터와함수.cpp

#include <stdio.h>
#include <stdlib.h>

int f(int *i, int j);
//함수에서 매개변수로 포인터를 받을 수 있다. 
//&x => 주소로 보내야 한다. 
//함수 전방선언. main이 인지를 못하니까. 

int main(void) {
	int x = 10, y = 20;
	printf("%d \n" , f(&x, y)); //51
	printf("%d %d\n" , x , y);//15, 20 

	return 0;
}

int f(int *i, int j){
	*i += 5;
	return (2 * *i + ++j);
}

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• _21_문제

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• 문제027_포인터와함수.cpp

#include <stdio.h>
#include <stdlib.h>

int f(int *i, int j);

int main(void) {
	int x = 10, y = 20;
	printf("%d \n" , f(&x, y));
	printf("%d %d\n" , x , y);

	return 0;
}

int f(int *i, int j){
	*i += 5;
	return (2 * *i + ++j);
}

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• 문제027_포인터와함수02.cpp

#include <stdio.h>
#include <stdlib.h>

int foo(int a, int *b);

int main(void) {
	int a = 5;
	int b = 3;
	int c = 0;
	b = foo(a , &c);
	printf("a = %d b = %d c = %d\n", a , b, c);
	c = foo(b , &a);
	printf("a = %d b = %d c = %d\n", a , b, c);
	return 0;
}

int foo(int a, int *b){
	int c;
	*b = a + 1;
	c = a - 1;
	return c;
}

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• 문제027_포인터와함수03.cpp

#include <stdio.h>
#include <stdlib.h>

void swap(int a, int *b);

int main(void) {
	int value = 3, list[4] = {1, 3, 5, 8};
	int i;
	
	swap(value , &list[0]);
	
	for (i = 0; i < 4; i++)
		printf("%d " , list[i]); //3 3 5 8 
	
	printf("\n");
	
	swap(list[2], &list[3]);
		
	for (i = 0; i < 4; i++)
		printf("%d " , list[i]); // 3 3 5 5 
	printf("\n");	
	
	swap(value, &list[value]);	
	
	for (i = 0; i < 4; i++)
		printf("%d " , list[i]); // 3 3 5 3 
	return 0;
}

void swap(int a, int *b){
	int temp;
	temp = a;
	a = *b;
	*b = temp;
}

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• 문제027_포인터와함수04.cpp

#include <stdio.h>
#include <stdlib.h>

void change(int *px, int* py, int pc, int pd);

int main(void) {
	int a = 10, b = 20, c = 30, d = 40;
	change(&a, &b, c, d);
	printf("%d %d %d %d", a , b, c, d); //60 70 30 40 
	return 0;
}

void change(int *px, int* py, int pc, int pd){
	*px = *py + pd; //20  + 40 = 60 
	*py =pc + pd; //70 
	pc = *px + pd; // 100
	pd = *px + *py; //
}

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