content
- 1. Creation and initialization of one-dimensional arrays
- 2. The use of one-dimensional arrays
- 3. Storage of one-dimensional arrays in memory
- 4. Creation and initialization of two-dimensional arrays
- 5. The use of two-dimensional arrays
- 6. Storage of two-dimensional arrays in memory
- 7. Array out of bounds
- 8. Arrays as function parameters
- 9. Teach you the group by hand
1. Creation and initialization of one-dimensional arrays
create: Take an integer array as an example
int arr[5] = {
1,2,3,4,5 };
The shape is like this, arrfor the created array name
[5], the array inside is the number of elements of the array,
intindicating that the type of the elements of the array is an integer type
initialization：
int arr[5] = {
1,2,3,4,5 };
这种是把数组里面的元素全部初始化，并且指定了数组元素的个数
int arr1[] = {
1,2,3,4,5 };
这种没有指定数组的个数，数组的元素的个数根据后面大括号里面的个数确定
int arr2[5] = {
1,2 };
这种指定了数组元素的大小却没有完全初始，
前面两个元素分别被初始化为1，2后面3个元素都被默认初始化为0
character array
char arr[]="maoleshua";
这是10个元素，因为字符串以\0为结尾
char arr[]={
'm','l','n','b'};
这是4个元素
think
int n=5;
int arr[n]={
1,2,3,4,5};
Is the above code correct? Before the C99 standard, it was wrong to write this way ( [] can only contain integer constants ), but after that, there is the concept of variable-length arrays, which is correct.
But the vs compiler does not support the C99 standard for the time being. So it is wrong.
2. The use of one-dimensional arrays
easy to use
int main()
{
int arr[5] = {
1,2 };
int i = 0;
for (i = 0; i < 5; i++)
{
arr[i] = i;
}
for (i = 0; i < 5; i++)
{
printf("%d ", arr[i]);
}
return 0;
}
3. Storage of one-dimensional arrays in memory
The array is stored contiguously in memory.
For the above code,
look at its memory address
4. Creation and initialization of two-dimensional arrays
The two-dimensional array looks like this int arr[][], the first [ ] represents the row, and the second [ ] represents the column.
initialization:
int arr1[2][2] = {
1,2,3 ,4};
全部初始化
int arr2[2][2] = {
{
1,2},{
3 ,4} };
和上面的一样，每个大括号表示一行
int arr3[2][2] = {
{
1},{
2,3 } };
这种第一行没有完全初始化，没有完全初始化的被默认初始化为0
int arr4[][2] = {
1,2,3 ,4};
这种省略行的表示是正确的，行数由后面的初始化的确定
int arr5[2][] = {
1,2,3,4 };
这种初始化是错误的，不能省略列
int arr6[2][2] = {
1 };
非完全初始化，其余元素都为0
5. The use of two-dimensional arrays
It's that simple to use
int arr[2][2] = {
1,2,3 ,4};
int i, j;
for(i=0;i<2;i++)
{
for (j=0;j<2;j++)
{
printf("%d ", arr[i][j]);
}
printf("\n");
}
6. Storage of two-dimensional arrays in memory
Two-dimensional arrays are also stored contiguously in memory
7. Array out of bounds
Array out of bounds means accessing memory outside the array.
Take a one-dimensional array as an example
int arr[5] = {
1,2 };
int i = 0;
for (i = 0; i < 6; i++)这里当i==5，访问数组中第6个元素，为越界访问
{
arr[i] = i;
}
8. Arrays as function parameters
The array name of a one-dimensional array represents the address of the first element . The array name of a two-dimensional array represents the address of the element of the
first row . Calculates the size of the entire array, in bytes
void f(int* arr)
{
int st = sizeof(arr) / sizeof(arr[0]);
大家可能以为st的值为5，但是为1，
因为这个arr是指针变量，32位平台上占4个字节
}
int main()
{
int arr[5] = {
1,2,3 ,4 };
f(arr);
return 0;
}
Readers must pay attention
9. Teach you the group by hand
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