An example of C implementing an indefinite array

When writing programs, we often need to define such an array, and the size of the array can only be known after the previous program runs. However, C language does not support the definition of indefinite array directly, but we can achieve an indefinite array through dynamic array.

1 dimensional array:

#include<stdio.h>
#include<stdlib.h>// In order to use malloc Is to include this header file 
#include <memory.h>// In order to use memset Is to include this header file 
int main()
{
 int m;
 scanf("%d", &m);//scanf It just ends when it hits a carriage return, and it doesn't enter a carriage return, so there's also a carriage return in the input stream 1 A carriage return 
 getchar();// Read the carriage return character in the input stream 
 int *p;
 p = (int*)malloc(m*(sizeof(int)));// Dynamic memory request 
 memset(p, 0, m);// Initialize, each element is zero 
 int i;
 for (i=0;i<m; i++)// Array assignment 
 {
  p[i] = i;
 }
  for (i = 0; i <m; i++)// Print the array 
  {
   printf("%d,", p[i]);
  }
 free(p);// Free memory 
 getchar();// Let the program pause so you can see the output 
 return 0;
}

2 dimensional indefinite array

#include <stdio.h>
#include <stdlib.h>// In order to use malloc Is to include this header file 
#include <memory.h>// In order to use memset Is to include this header file 
int main()
{
 int m, n;
 scanf("%d%d", &m,&n);//scanf It just ends when it hits a carriage return, and it doesn't enter a carriage return, so there's also a carriage return in the input stream 1 A carriage return 
 getchar();// Read the carriage return character in the input stream 
 int **p;
 p = (int**)malloc(m*(sizeof(int*)));//2 The address where the level pointer resides applies to memory 
 int i, j;
 for (i = 0; i<m; i++)
  p[i] = (int*)malloc(sizeof(int)*n);//1 The address where the level pointer resides applies to memory 
 for (i = 0; i < m; i++)
  for (j = 0; j < n; j++)
   p[i][j] = i + j;
 for (i = 0; i < m; i++)
 {
  for (j = 0; j < n; j++)
  {
   printf("%d %p ", p[i][j], &p[i][j]);  // The output of each element and address, the address between the columns of each row is continuous, the address between the rows is discontinuous  
  }
  printf("\n");
 }
 for (i = 0; i < m; i++) free(p[i]);  
 free(p);
 getchar();// Let the program pause so you can see the output 
 return 0;
}