My personal understanding about pointer arrays and pointer arrays in C language, pointer Arrays

My personal understanding about pointer arrays and pointer arrays in C language, pointer Arrays

I. pointer array and pointer Array

　　1. pointer Array

As the name suggests, an element is an array of all pointers. Its form is similar to that of a common array, for example, * a [N].

Before understanding how to use pointer arrays, let me explain my personal understanding of arrays.

For example, a one-dimensional integer array (such as int a [3]) is actually a variable with three integer elements; a two-dimensional integer array (such as int a [4] [3]) can be considered as composed of a [4] and int [3, consider a [4] as a one-dimensional array, which contains a [0], a [1], a [2], a [3], each element is of the int [3] type. For example, a [0] contains a [0] [0], a [0] [1], a [0] [2] Three elements; 3D arrays and so on...

Since the element of the pointer array is a pointer, each element of the pointer array can point to other elements of the same type (for example, to an array ).

The following example shows how to use a pointer array.

1 # include <stdio. h> 2 # include <stdlib. h> 3 4 # define M 4 5 # define N 3 6 7 void main () 8 {9 int * a [M], B [M] [N]; // define the pointer array and the two-dimensional array respectively. 10 int I, j; 11 12 for (I = 0; I <M; I ++) // assign values to the array 13 {14 for (j = 0; j <N; j ++) 15 {16 B [I] [j] = I + j; 17} 18} 19 20 for (I = 0; I <M; I ++) // assign a value to the pointer array, point the element to element 21 {22 a [I] = B [I]; 23} 24 25 for (I = 0; I <M; I ++) // print the array 26 {27 for (j = 0; j <N; j ++) 28 {29 printf ("% 4d ", a [I] [j]); // a [I] [j] can be written as * (a [I] + j) other reasonable formats such as 30} 31 printf ("\ n"); 32} 33 34 35 getchar (); 36}

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2. array pointer

An array pointer is a pointer to an array in the form of (* a) [N]. It can point either to a one-dimensional array or to a two-dimensional array. When the + 1 operation is performed, it will span N Units.

The following is an example.

1 # include <stdio. h> 2 # include <stdlib. h> 3 # define M 4 4 # define N 3 5 6 7 void main () 8 {9 int (* a) [N], B [M] [N]; 10 int I, j; 11 12 for (I = 0; I <M; I ++) 13 {14 for (j = 0; j <N; j ++) 15 {16 B [I] [j] = I + j; 17} 18} 19 20 21 printf ("Print array \ n" Using B [I] [j]); 22 for (I = 0; I <M; I ++) 23 {24 for (j = 0; j <N; j ++) 25 {26 printf ("% 4d", B [I] [j]); 27} 28 printf ("\ n"); 29} 30 31 a = & B [0]; // or a = B, but the former may be more accurate 32 33 printf ("using a [I] [j] to print the array \ n"); 34 for (I = 0; I <M; I ++) 35 {36 for (j = 0; j <N; j ++) 37 {38 printf ("% 4d", a [I] [j]); 39} 40 printf ("\ n"); 41} 42 43 getchar (); 44}

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