C ++ pointer array and pointer to pointer

Pointer Array

 

Definition:
If an array contains all pointer-type data, the array is a pointer array, that is, each element in the pointer array is equivalent to a pointer variable, and its value is an address.

 

Form:
The definition of a one-dimensional pointer array is as follows:

Int [type name] * p [array name] [4] [array length ];

Because [] is higher than *, p is first combined with [4] to form an array of p [4. Then it is combined with "*" before p. "*" indicates that the array is of the pointer type. Each array element is equivalent to a pointer variable and can point to an integer variable.

Note: it cannot be written as int (* p) [4]. This refers to a pointer variable pointing to a one-dimensional array.

Use each element in the pointer array to point to several strings respectively to make string processing more flexible.

Program 1.1

 

#include<iostream>  using namespace std; int main(){     void sort(char *p[],int n);     void print(char *p[],int n);     char *name[]={"C","C++","PHP","ASP","ASP.NET","C#","JAVA","BASIC","PASCAL","COBOL"};     int n=10;     sort(name,n);     print(name,n);     return 0; } void sort(char *p[],int n){     char *temp;     int i,j,k;     for(i=0;i<n;i++){         k=i;         for(j=i;j<n;j++){             if(strcmp(p[j],p[k])<0){                 k=j;             }         }         if(k!=i){             temp=p[k];             p[k]=p[i];             p[i]=temp;         }     } } void print(char *p[],int n){     int i;     for(i=0;i<n;i++){         cout<<p[i]<<endl;     } } #include<iostream>using namespace std;int main(){ void sort(char *p[],int n); void print(char *p[],int n); char *name[]={"C","C++","PHP","ASP","ASP.NET","C#","JAVA","BASIC","PASCAL","COBOL"}; int n=10; sort(name,n); print(name,n); return 0;}void sort(char *p[],int n){ char *temp; int i,j,k; for(i=0;i<n;i++){  k=i;  for(j=i;j<n;j++){   if(strcmp(p[j],p[k])<0){    k=j;   }  }  if(k!=i){      temp=p[k];      p[k]=p[i];      p[i]=temp;  } }}void print(char *p[],int n){ int i; for(i=0;i<n;i++){  cout<<p[i]<<endl; }}

 
 

Analysis:
The main function defines the pointer array name. Its ten elements are strings.

 

"C","C++","PHP","ASP","ASP.NET","C#","JAVA","BASIC","PASCAL","COBOL" "C","C++","PHP","ASP","ASP.NET","C#","JAVA","BASIC","PASCAL","COBOL"

. Then, the address of the first element of the array is uploaded to the p array in the sort function. Therefore, the form parameter p and the real parameter name point to the same array. Then, the array is sorted by the selection method.

The print function outputs each string, p [0] ~ P [9] is the first address of each string.

The print function can also be rewritten as follows:

 

void print(char *p[],int n){     char *q=p[0];     int i=0;     while(i<n){         q=*(p+i++);         cout<<q<<endl;     } } void print(char *p[],int n){    char *q=p[0];    int i=0;    while(i<n){     q=*(p+i++);     cout<<q<<endl;    }}

Pointer to pointer

 

Definition:

The pointer to the pointer data is the pointer to the pointer, for example, the pointer array name [10] defined in main function of program 1.1.

 

 

Char ** p = name indicates that the address of the first pointer element in the pointer array is assigned to the variable p pointing to the pointer;

Program 1.2

 

Include <iostream> using namespace std; int main () {char * name [] = {"C", "C ++", "PHP", "ASP ", "ASP. NET "," C # "," JAVA "," BASIC "," PASCAL "," COBOL "}; char ** p; p = name + 2; cout <p <endl; cout <* p <endl; // equivalent to name [2] cout <** p <endl; return 0 ;} # include <iostream> using namespace std; int main () {char * name [] = {"C", "C ++", "PHP", "ASP ", "ASP. NET "," C # "," JAVA "," BASIC "," PASCAL "," COBOL "}; char ** p; p = name + 2; cout <p <endl; cout <* p <endl; // equivalent to name [2] cout <** p <endl; return 0 ;}

#

Analysis:

P is the pointer to the pointer, that is, the value of the address of the stored name [2;

* P is the pointer, that is, the value of name [2] (element in the pointer array );

** P indicates the data value pointed to by the pointer. Because the defined p indicates data of the char type, the first character is output.