c语言数组

 

#include <stdio.h>
#include <string.h>
void main() {
    int a[3] = {1, 2, 3}; 
    int *p; 
    int (*s)[3];
    p = a;  // one dimensional array avaialbe is like a int* type
    s = &a; 
    printf("%d\n", *(p + 1)); // 2
    p = (int*) (&a[0] + 1); 
    printf("%d\n", *(p - 1)); //  1 
    p = (int*) (a + 1); 
    printf("%d\n", *(p - 1)); // 1
    p = (int*) (&a + 1); 
    printf("%d\n", *(p - 1)); // 3

    int b[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    int **q;
    //q = b; // compile error
    s = b;  
    printf("s[2][2] = %d\n", s[2][2]); // 9 
    printf("*(*(s + 1) + 1) = %d\n", *(*(s + 1) + 1)); // 5
    printf("size:%lu\n", sizeof(b[1])); // 12
    p = (int *)b[1];
    printf("%d\n", *p); // 4
    //printf("%d\n", *b);    // compile error
    //printf("%d\n", b[0]);  // compile error
    printf("*b[1] = %d\n", *b[1]);  // 4
    printf("**b = %d\n", **b); // 1
    //printf("%d\n", *(b + 1)); // compile error
    printf("**(b + 1) = %d\n", **(b + 1)); // 4
    printf("%d\n", *(*(b + 1) + 1));  // 5
    p = (int *)(&b + 1); 
    printf("%d\n", *(p - 1));  // 9 
}

int a[]; 一维数组类似于指针, 本质上和一个int类型的指针很像

int a[][];二维数组类似于指向一维数组的指针和指针的组合。指向一维数组的指针用于检索行。

#include <stdio.h>
#include <string.h>
void main() {
    const char *s = "12345";
    char a[] = "12345";

    a[3] = 'x';
    //s[3] = 'x'; // compile error
    printf("%s\n", a); 
    printf("sizeof(s) = %lu\n", sizeof(s)); // 8
    printf("sizeof(a) = %lu\n", sizeof(a)); // 6
}