Comments on several application methods of C ++ two-dimensional array new

In C ++ programming language, there is a two-dimensional array called new. It is used in a flexible way and can be used in many ways to help us implement some specific functions. Here, we will summarize several application methods of the C ++ two-dimensional array new to review them one by one.

C ++ two-dimensional array new Application Method 1:

 
 

  
  
A (*ga)[n] = new A[m][n];   
  
  
...   
  
  
delete []ga;  
 
 

Disadvantage: n must be known

Advantages: intuitive calling, continuous storage, and simple program (tested, the Destructor can be correctly called)

C ++ two-dimensional array new Application Method 2:

 
 

  
  
A** ga = new A*[m];   
  
  
for(int i = 0; i < m; i++)   
  
  
ga[i] = new A[n];   
  
  
...   
  
  
for(int i = 0; i < m; i++)   
  
  
delete []ga[i];   
  
  
delete []ga;  
 
 

Disadvantages: non-continuous storage, cumbersome procedures, ga is A ** type

Advantage: The call is intuitive. n can be unknown.

C ++ two-dimensional array new Application Method 3:

 
 

  
  
A* ga = new A[m*n];   
  
  
...   
  
  
delete []ga;  
 
 

Disadvantage: The call is not intuitive enough.

Advantage: continuous storage, n can be unknown

C ++ two-dimensional array new Application Method 4:

 
 

  
  
Vector> ga;
  
  
Ga. resize (m); // these three rows can be used
  
  
For (int I = 1; I <n; I ++ )//
  
  
Ga [I]. resize (n );//
  
  
...
 
 

Disadvantages: non-continuous storage, inconvenient debugging, lower Compilation speed, and program expansion (the actual speed is not much different)

Advantage: intuitive call, automatic analysis and memory release, can call stl related functions, dynamic growth

C ++ two-dimensional array new Application Method 5:

 
 

  
  
vector ga;   
  
  
ga.resize(m*n);  
 
 

Combination of method 3 and 4

C ++ two-dimensional array new Application Method 6:

Release Version 2

 
 

  
  
A** ga = new A*[m];   
  
  
ga[0] = new A[m*n];   
  
  
for(int i = 1; i < m; i++)   
  
  
ga[i] = ga[i-1]+n;  
 
 

Advantage: continuous storage, n can be unknown, and the structure is convenient. We only need to delete [] ga;