An array is a collection of elements of the same type
one-dimensional array
Creation of one-dimensional arrays
How to create a one-dimensional array
type_t arr_name[const_n];
//type_t 指一维数组的元素类型
//const_n 是一个常量表达式，用来指定一维数组的大小Instances created by one-dimensional arrays
//代码1
int arr1[10];
char arr2[10];
float arr3[10];
double arr4[10];
//代码2
int count = 10;
int arr5[count]; //数组无法正常创建
//数组的创建，[]中要给一个常量，不能使用变量Initialization of a one-dimensional array
//在创建一维数组的同时给一维数组的内容一些合理的初始值
int arr1[10] = {1, 2, 3}
int arr2[5] = {1, 2, 3, 4, 5}
//在创建一维数组时若不想指定一维数组的大小就得到初始化，一维数组的元素个数根据初始化的内容来确定
char arr3[] = "abc"; //'\0'会自动放入
char arr4[] = {'a', 'b','c'}; //不会出现'\0'
char *p = "abcdef"; //产生的是首字符的地址Use of one-dimensional arrays
#include <stdio.h>
int main()
{
int arr[10] = { 0 }; //数组的不完全初始化
//数组是使用下标来访问的，下标从0开始
int i = 0; //做下标
int sz = sizeof(arr) / sizeof(arr[0]);
for (i = 0; i < sz; i++)
{
arr[i] = i;
}
for (i = 0; i < 10; i++)
{
printf("%d ", arr[i]);
}
return 0;
}Summarize
- Arrays are accessed using subscripts, which start at 0.
- The size of the array can be calculated.
One-dimensional array storage in memory
As the index of the array grows, the address of the element also increases regularly. Therefore, arrays are stored contiguously in memory.
Pointer access to one-dimensional arrays
#include <stdio.h>
int main()
{
int arr[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
printf("%p\n", arr); //输出地址
printf("%d\n", *arr); //输出 1
return 0;
}
//由此可见，数组的数组名其实是数组首元素的地址
#include <stdio.h>
int main()
{
int arr[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
int i = 0;
int sz = sizeof(arr) / sizeof(arr[0]);
for (i = 0; i < sz; i++)
{
printf("&arr[%d] = %p\n", i, &arr[i]); //获取数组每个元素的地址
printf("%p\n", arr+i);
}
return 0;
}
//通过对数组名+整数的计算，其实我们可以获取到数组每个元素的地址
//使用指针访问数组
#include <stdio.h>
int main()
{
int arr[10] = { 0 };
int i = 0;
int *p_arr = arr;
int sz = sizeof(arr) / sizeof(arr[0]);
for (i = 0; i < sz; i++)
{
*(p_arr + i) = i;
}
for (i = 0; i < sz; i++)
{
printf("%d\n", *(p_arr + i));
}
return 0;
}Two-dimensional array
Creation of a two-dimensional array
int arr[3][4];
char arr[3][4];
double arr[3][4];Initialization of a two-dimensional array
int arr[3][4] = {1, 2, 3, 4};
int arr[3][4] = {{1, 2}, {3, 4}};
double arr[][4] = {{1, 2}, {3, 4}}; //可以不输入行号The use of two-dimensional arrays
#include <stdio.h>
int main()
{
int arr[3][4] = { 0 }; //二维数组的创建
int i = 0;
for (i = 0; i < 3; i++) //二维数组的初始化
{
int j = 0;
for (j = 0; j < 4; j++)
{
arr[i][j] = i * 4 + j;
}
}
for (i = 0; i < 3; i++)
{
int j = 0;
for (j = 0; j < 4; j++)
{
printf("%d ", arr[i][j]);
}
}
return 0;
}Two-dimensional array storage in memory
Two-dimensional arrays are also stored contiguously in memory
Pointer access to a two-dimensional array
#include <stdio.h>
#include <windows.h>
int main()
{
int arr[3][4] = { 0 };
int *p = &arr[0][0];
int i = 0;
for (i = 0; i < 3*4; i++)
{
*(p + i) = i;
}
for (i = 0; i < 3; i++)
{
int j = 0;
for (j = 0; j < 4; j++)
{
printf("%d ", arr[i][j]);
}
}
system("pause");
return 0;
}Calculations on Arrays
one-dimensional array
int arr[] = { 1, 2, 3, 4 };
printf("%d\n", sizeof(arr)); //16 整个数组的长度
printf("%d\n", sizeof(arr + 0)); //4 首元素的地址的长度
printf("%d\n", sizeof(*arr)); //4 首元素的长度
printf("%d\n", sizeof(arr + 1)); //4 第二个元素的地址的长度
printf("%d\n", sizeof(arr[1])); //4 第二个元素的长度
printf("%d\n", sizeof(&arr)); //4 数组的地址的长度
printf("%d\n", sizeof(*&arr)); //16 整个数组的长度
printf("%d\n", sizeof(&arr + 1)); //4 跳过整个数组后的第一个地址的长度
printf("%d\n", sizeof(&arr[0])); //4 首元素地址的长度
printf("%d\n", sizeof(&arr[0] + 1)); //4 第二个元素的地址的长度character array
char arr[] = { 'a', 'b', 'c', 'd', 'e', 'f' }; //字符数组一个元素只有一个字节
printf("%d\n", sizeof(arr)); //6 整个数组的长度
printf("%d\n", sizeof(arr + 0)); //4 首元素的地址的长度
printf("%d\n", sizeof(*arr)); //1 首元素的长度
printf("%d\n", sizeof(arr[1])); //1 第二个元素的长度
printf("%d\n", sizeof(&arr)); //4
printf("%d\n", sizeof(&arr + 1)); //4 跳过整个数组后的第一个地址的长度
printf("%d\n", sizeof(&arr[0] + 1)); //4 第二个元素的地址的长度
printf("%d\n", strlen(arr)); //随机值
printf("%d\n", strlen(arr + 0)); //随机值
printf("%d\n", strlen(*arr)); //报错
printf("%d\n", strlen(arr[1])); //报错
printf("%d\n", strlen(&arr)); //随机值
printf("%d\n", strlen(&arr + 1)); //随机值
printf("%d\n", strlen(&arr[0] + 1)); //随机值
char arr[] = "abcdef";
printf("%d\n", sizeof(arr)); //7 整个数组的长度
printf("%d\n", sizeof(arr + 0)); //4 首元素的地址的长度
printf("%d\n", sizeof(*arr)); //1 首元素的长度
printf("%d\n", sizeof(arr[1])); //1 第二个元素的长度
printf("%d\n", sizeof(&arr)); //4
printf("%d\n", sizeof(&arr + 1)); //4 跳过整个数组后的第一个地址的长度
printf("%d\n", sizeof(&arr[0] + 1)); //4 第二个元素的地址的长度
printf("%d\n", strlen(arr)); //6
printf("%d\n", strlen(arr + 0)); //6
printf("%d\n", strlen(*arr)); //报错
printf("%d\n", strlen(arr[1])); //报错
printf("%d\n", strlen(&arr)); //6
printf("%d\n", strlen(&arr + 1)); //报错
printf("%d\n", strlen(&arr[0] + 1)); //5
char *p = "abcdef";
printf("%d\n", sizeof(p)); //4
printf("%d\n", sizeof(p + 1)); //4
printf("%d\n", sizeof(*p)); //1
printf("%d\n", sizeof(p[0])); //1
printf("%d\n", sizeof(&p)); //4 p的地址
printf("%d\n", sizeof(&p + 1)); //4 p的下一个地址
printf("%d\n", sizeof(&p[0] + 1)); //4
printf("%d\n", strlen(p)); //6
printf("%d\n", strlen(p + 1)); //5
printf("%d\n", strlen(*p)); //报错
printf("%d\n", strlen(p[0])); //报错
printf("%d\n", strlen(&p)); //随机值
printf("%d\n", strlen(&p + 1)); //随机值
printf("%d\n", strlen(&p[0] + 1)); //5Two-dimensional array
int arr[3][4] = { 0 };
printf("%d\n", sizeof(arr)); //48 整个数组的长度
printf("%d\n", sizeof(arr[0][0])); //4 首元素的长度
printf("%d\n", sizeof(arr[0])); //16 第一行的长度
printf("%d\n", sizeof(arr[0]+1)); //4 第一行第二个元素的长度
printf("%d\n", sizeof(arr+1)); //4
printf("%d\n", sizeof(&arr[0] + 1)); //4 第二行的地址的长度
printf("%d\n", sizeof(*arr)); //16 第一行的长度的长度
printf("%d\n", sizeof(arr[3])); //16 最后一行的长度Summarize
- The array name is placed inside sizeof alone, and the array name represents the entire array.
- The & array name takes out the address of the entire array, and the array name represents the entire array.
All array names other than that represent the address of the first element of the array.
array as function parameter
When an array is used as a function parameter, the entire array is not passed. In fact, only the address of the first element of the array is passed, so even if it is written in the form of an array in the function parameter part: int arr[ ] is still a pointer: int arr.