C基础--二重指针和数组指针

#include <stdio.h>

int main1(void)
{
    int a = 3;
    int b = 8;
    int *p = &a;  // int*  p = &a;
    int **q;        // int**  q;
    q = &p;
    **q = 10;
    *q =  &b;
    **q = 5;
    p = &b;
    *p = 9;

    printf("a = %d\tb = %d\n", a, b);

    return 0;
}

//void fun(char *arr[], int n)
void fun(char **arr, int n)        //二重指针传参时等价于指针数组
{
    int i;
    for (i = 0; i < n; i++)
        printf("%s\n", arr[i]);
        //printf("%s\n", *(arr+i));        //当成二重指针去索引元素
}
int main(void)
{
    char *s[3] = {"hello", "world", "xwp"};
    fun(s, 3);
    return 0;
}

#include <stdio.h>

int main1(void)
{
    int a[10] = {1,2,3,4,5,6,7,8,9,0};
    //int *p;
    int (*p)[10];    //先算小括号，p和*结合，属于指针类型，指针指向拥有10个int型元素的数组
    //p = a;        int *p; p = a;            a + 1
    p = &a;            //int (*p)[10] = &a;   &a + 1        p+1  加过40个字节

    printf("%d\t%d\n", sizeof(p), sizeof(*p));
    printf("%d\n", (*p)[3]);

    return 0;
}

int main2(void)
{
    /*
    char str[3][20] = {"hello", "world", "itcast"};
    char (*p)[20];

    p = &str[0];
    printf("%s\n", *(p+1));
    */
/*
    char str[3][20] = {"hello", "world", "itcast"};
    char *p;

    p = str[0];
    //printf("%s\n", p);
    printf("%s\n", (p+20));
    */
    char str[3][20] = {"hello", "world", "itcast"};
    char (*p)[20];
    p = str;
    printf("%s\n", *(p+1));
    return 0;
}
//void fun(char a[][20], int n)    //数组指针传参时等价于二维数组
void fun(char (*a)[20], int n)
{
    int i;
    for (i = 0; i < n; i++)
        scanf("%s", a[i]);
    return;
}
int main(void)
{
    int i;
    char s[3][20];
    fun(s, 3);
    for (i = 0; i < 3; i++)
        printf("%s\n", s[i]);

    return 0;
}