How to operate a two-dimensional array with level two pointers in C language

Accessing a two-dimensional array through a level two pointer requires assigning a one-dimensional array pointer equal to the number of rows in a two-dimensional array, and then assigning each header of a two-dimensional array to a one-dimensional pointer in the corresponding position. It can then be accessed directly by a two-dimensional pointer.

Refer to the code below, you can see the specific annotation auxiliary understanding.

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#include <stdio.h>//输入输出头文件。#include <stdlib.h>//本程序需要用到malloc/free函数，引用该头文件。intmain(){    int a[3][4] = {1,2,3,4,5,6,7,8,9,10,11,12}; //定义二维数组a，并赋值从1-12.    int** p = NULL;//定义二维指针。    inti, j;        p = (int**)malloc(sizeof(int*) *3);//要访问的数组有三行，所以申请三个一维指针变量。    for(i = 0; i < 3; i ++)    {        p[i] = a[i];//将二维数组行地址赋值到对应的一维指针上。    }        for(i = 0; i < 3; i ++)    {        for(j = 0; j < 4; j ++)            printf("%d ", p[i][j]); //用指针输出元素。p[i][j]这里也可以写作*(*(p+i) + j)。        printf("\n"); //每行输出后加一个换行    }        free(p);//释放申请的内存。        return0;}

Using two-dimensional pointers to access two-dimensional arrays is used for function calls.

For a one-dimensional array, if the function parameter is a one-dimensional pointer, the array name can be used directly as a function parameter. However, if the function parameter is a two-dimensional pointer, the direct use of two-dimensional array names to make the parameter access error occurs because the two-dimensional pointers and two-dimensional arrays are accessed differently, you need to do the conversion in the sample code.

Another common method is to use the memory continuity of a two-dimensional array to convert a two-dimensional array to a one-dimensional array, regardless of the subject matter, without any further description.

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How to operate a two-dimensional array with level two pointers in C language