[c/cpp]：指针的区别：【 int *px[3] 和 int (*pa)[3] 】

[c/cpp]：指针的区别：【 int *px[3] 和 int (*pa)[3] 】

 

 

 

 

一、程序代码

 

#include <iostream>


int msg()
{
    int x[3] = {1,2,3};
    
    int xx[4][3] = {
        {1,2,3},
        {4,5,6},
        {7,8,9},
        {10,11,12}
    };
    

    //  'px' is an array with three int pointers
    int* px[3];
    px[0] = &x[0];
    px[1] = &x[1];
    px[2] = &x[2];
    //std::cout << "\t[p2x][2]_value  \t:=\t" << *px[2] << std::endl;
    //std::cout << "\t[p2x][2]_address\t:=\t" <<  px[2] << std::endl;

    
    //  'pa' points to an array with three int elements;
    int (*pa)[3];
    //pa = &x;
    pa = xx;
    //std::cout << "\t[p2a]_value  \t:=\t" <<  pa[0][2] << std::endl;
    //std::cout << "\t[p2a]_address\t:=\t" << &pa[0][2] << std::endl;


    // test output: general ouput
    for (int i=0; i<3; i++) {
        std::cout << "\n" << "element_general["<< i <<"]" << std::endl;
        std::cout << "\t[p2x][" << i << "]_value  \t:=\t" << *px[i] << std::endl;
        std::cout << "\t[p2x][" << i << "]_address\t:=\t" <<  px[i] << std::endl;
        std::cout << "\t[p2a][0][" << i << "]_value  \t:=\t" <<  pa[0][i] << std::endl;
        std::cout << "\t[p2a][0][" << i << "]_address\t:=\t" << &pa[0][i] << std::endl;
    }

    //  test ouput2: array output
    std::cout << "\n\n" << "------------------------" << std::endl;
    for ( int i=0; i<4; i++) {
        std::cout << "\nelement_array[" << i << "]" << std::endl;
        for ( int j=0; j<3; j++) {
            std::cout << "\tpa[" << i << "][" << j << "]_value  \t:=\t" <<  pa[i][j] << std::endl;
            std::cout << "\tpa[" << i << "][" << j << "]_address\t:=\t" << &pa[i][j] << std::endl;
        }
    }
    
    // test ouput3: pointer output
    std::cout << "\n\n" << "------------------------" << std::endl;
    pa=xx;
    for ( int i=0; i<4; i++, pa++) {
        std::cout << "\nelement_pointer[" << i << "]" << std::endl;
        for ( int j=0; j<3; j++) {
            std::cout << "\tpa[" << i << "][" << j << "]_value  \t:=\t" <<  pa[0][j] << std::endl;
            std::cout << "\tpa[" << i << "][" << j << "]_address\t:=\t" << &pa[0][j] << std::endl;
        }
        
    }
    
    
    return 0;
}


int main (int argc, char* argv[], char* envp[])
{
    msg();
    
    return 0;
}

 

 

 

 

二、运行结果

 

element_general[0]
	[p2x][0]_value  	:=	1
	[p2x][0]_address	:=	0x7fff4a706c80
	[p2a][0][0]_value  	:=	1
	[p2a][0][0]_address	:=	0x7fff4a706cb0

element_general[1]
	[p2x][1]_value  	:=	2
	[p2x][1]_address	:=	0x7fff4a706c84
	[p2a][0][1]_value  	:=	2
	[p2a][0][1]_address	:=	0x7fff4a706cb4

element_general[2]
	[p2x][2]_value  	:=	3
	[p2x][2]_address	:=	0x7fff4a706c88
	[p2a][0][2]_value  	:=	3
	[p2a][0][2]_address	:=	0x7fff4a706cb8


------------------------

element_array[0]
	pa[0][0]_value  	:=	1
	pa[0][0]_address	:=	0x7fff4a706cb0
	pa[0][1]_value  	:=	2
	pa[0][1]_address	:=	0x7fff4a706cb4
	pa[0][2]_value  	:=	3
	pa[0][2]_address	:=	0x7fff4a706cb8

element_array[1]
	pa[1][0]_value  	:=	4
	pa[1][0]_address	:=	0x7fff4a706cbc
	pa[1][1]_value  	:=	5
	pa[1][1]_address	:=	0x7fff4a706cc0
	pa[1][2]_value  	:=	6
	pa[1][2]_address	:=	0x7fff4a706cc4

element_array[2]
	pa[2][0]_value  	:=	7
	pa[2][0]_address	:=	0x7fff4a706cc8
	pa[2][1]_value  	:=	8
	pa[2][1]_address	:=	0x7fff4a706ccc
	pa[2][2]_value  	:=	9
	pa[2][2]_address	:=	0x7fff4a706cd0

element_array[3]
	pa[3][0]_value  	:=	10
	pa[3][0]_address	:=	0x7fff4a706cd4
	pa[3][1]_value  	:=	11
	pa[3][1]_address	:=	0x7fff4a706cd8
	pa[3][2]_value  	:=	12
	pa[3][2]_address	:=	0x7fff4a706cdc


------------------------

element_pointer[0]
	pa[0][0]_value  	:=	1
	pa[0][0]_address	:=	0x7fff4a706cb0
	pa[0][1]_value  	:=	2
	pa[0][1]_address	:=	0x7fff4a706cb4
	pa[0][2]_value  	:=	3
	pa[0][2]_address	:=	0x7fff4a706cb8

element_pointer[1]
	pa[1][0]_value  	:=	4
	pa[1][0]_address	:=	0x7fff4a706cbc
	pa[1][1]_value  	:=	5
	pa[1][1]_address	:=	0x7fff4a706cc0
	pa[1][2]_value  	:=	6
	pa[1][2]_address	:=	0x7fff4a706cc4

element_pointer[2]
	pa[2][0]_value  	:=	7
	pa[2][0]_address	:=	0x7fff4a706cc8
	pa[2][1]_value  	:=	8
	pa[2][1]_address	:=	0x7fff4a706ccc
	pa[2][2]_value  	:=	9
	pa[2][2]_address	:=	0x7fff4a706cd0

element_pointer[3]
	pa[3][0]_value  	:=	10
	pa[3][0]_address	:=	0x7fff4a706cd4
	pa[3][1]_value  	:=	11
	pa[3][1]_address	:=	0x7fff4a706cd8
	pa[3][2]_value  	:=	12
	pa[3][2]_address	:=	0x7fff4a706cdc



g++ -std=c++20 -O2 -Wall -pedantic -pthread main.cpp && ./a.out

 

 

 

 

三、参考资料

 

　　1、　　cpp 在线编译器　　-　　https://coliru.stacked-crooked.com/