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

Source: Internet
Author: User

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:

 
 
  1. A (*ga)[n] = new A[m][n];   
  2. ...   
  3. 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:

 
 
  1. A** ga = new A*[m];   
  2. for(int i = 0; i < m; i++)   
  3. ga[i] = new A[n];   
  4. ...   
  5. for(int i = 0; i < m; i++)   
  6. delete []ga[i];   
  7. 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:

 
 
  1. A* ga = new A[m*n];   
  2. ...   
  3. delete []ga;  

Disadvantage: The call is not intuitive enough.

Advantage: continuous storage, n can be unknown

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

 
 
  1. Vector> ga;
  2. Ga. resize (m); // these three rows can be used
  3. For (int I = 1; I <n; I ++ )//
  4. Ga [I]. resize (n );//
  5. ...

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:

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

Combination of method 3 and 4

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

Release Version 2

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

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

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