Two-dimensional arrays

Two-dimensional array definitions:

General form: type specifier array name [constant expression 1][constant expression 2]

int a[2][3];

　

Using the C + + STL vector definition:

vector< vector<int> > Array (2, vector<int> (0)); Define the number of rows as 2

for (int i=0; i<2; i++)

Array[i].resize (3); Defines the number of columns as 3

　　　　

Initialization of two-dimensional arrays:

Fragment assignment: int a[2[3]={{1, 2, 3},{4, 5, 6}}//row of constant expression can be omitted;

Continuous assignment: int a[2[3]={1, 2, 3, 4}//partial element assignment, followed by automatic assignment of 0

Parameter passing for two-dimensional arrays:

void Fun (int a[][3]) {...} Note that array a passes the parameter and then degenerates to a pointer

Dynamic allocation and release of two-dimensional arrays:

int **a=new int*[2];

for (int i=0; i<2; i++) {

A[i]=new Int[3];

}

////////////////////////////

for (int i=0; i<2; i++) {

Delete[] a[i];

}

Delete[] A;

Pointers to two-dimensional arrays:

int **p=a; Pointer P equals a

*p <=> a[0];  * (p+i) <=> a[i]; * (* (p+i) +j) <=> A[i][j]

Row and column calculations for two-dimensional arrays:

Total size: t=sizeof (a)/sizeof (A[0][0])

Number of columns: n=sizeof (a[0])/sizeof (a[0][0]); Array[0].size ()//vector type requires deep "inside" to find the size of the column

Number of rows: m=t/n; Array.size ()//vector type can directly find the size of the row

Two-dimensional arrays