An example of the application of a two-dimensional pointer to an array pointer

In fact, the multidimensional array of the computer system is actually finally implemented in the form of a one-dimensional array. In terms of a two-dimensional array of n x m, set its array to be named array. The pointer array points to an array that holds a series of pointers that point to the corresponding one-dimensional array, where our data is stored.

This array

is the I-pointer variable address, ARRAY[J] that is relative to the I-pointer variable offset j*sizeof (array type). Through this mechanism, the system accesses the contents of line I of the two-dimensional array and the column J. As you know, a pointer to a two-dimensional array is actually a pointer variable that points to the pointer variable address. So when you declare a pointer to a two-dimensional array, use the form int * * as array.

int main () {
int a[n][n];
for (int i=0;i<n;i++) {
for (int j=0;j<n;j++) {
A[i][j]=i*n+j;
}
}
for (int i=0;i<n;i++)
cout<<* (* (a+i)) <<endl;
}

A two-dimensional array is actually a two-dimensional array pointer, and the output of this program is: 0 3 6

int main () {
int a[n][n];
for (int i=0;i<n;i++) {
for (int j=0;j<n;j++) {
A[i][j]=i*n+j;
}
}
for (int i=0;i<n;i++) {
for (int j=0;j<n;j++) {

cout<<* (* (a+i) +j) <<endl;

}
}
}

Here A is a pointer to the pointer, this function iterates through the entire array according to the line precedence, which is very well understood, * (A+i) represents the first address of line I, * (A+i) +j represents the address of the J element of line I, * (* (a+i) +j) denotes the element of row I, Column J, So we can iterate over the entire array. This is the line-first traversal of the array.

int main () {
int a[n][n];
for (int i=0;i<n;i++) {
for (int j=0;j<n;j++) {
A[i][j]=i*n+j;
}
}
for (int i=0;i<n;i++) {
for (int j=0;j<n;j++) {

cout<<* (* (a+j) +i) <<endl;

}
}
}

This is a column-first traversal of an array.

An example of the application of a two-dimensional pointer to an array pointer