Pointer Study Notes

A pointer variable definition

type *name;

Here, '*' to represent him is a pointer variable.

Second, the pointer assignment

int *p=nullptr;

Here, nullptr is a null pointer

int a=2;

p=&a;

'&' Character to take the address (which is often used in scanf) to pass a pointer to the address p, where a must int. Obviously, the p-direct access, the address operation. If the operation must be added to the indirect pointer operator '*'.

note!

1, can not assign a pointer variable number

2, the pointer variable can not add '*' address when want to change

3, printf ( "% d", p); output the address pointer, and printf ( "% d", * p); pointer value is output

Pointer variable with ordinary variables, and assignment to be defined before use. As defined int a; int * p = & a; then, P is stored in the starting address of a occupied cells, * p and a are the same, so printf ( "% d", * p); equal to printf ( "% d", a);

Example 1

problem B + A (pointer Edition)

#include <cstdio>
 the using  namespace STD;
 int main () {
     int A, B, P1 *, P2 *;   // declaration of a general variable and pointer 
    P1 = & A;   // pointer variable assignment 
    P2 = & B;   
    Scanf ( " % % D D " , P1, p2);   // P1 and p2 are directly stored address, the addresses do not have to take 
    the printf ( " % D " , * * P1 + p2);   // fetch address by adding the contents of 
    return  0 ; 
}

Third, the addition and subtraction pointer variable

Pointer only supports two modes of operation! + And -, and the general operation of the array with

Example 2

Tao Tao picking apples (pointer version)

Title Description https://www.luogu.org/problemnew/show/P1046

#include <cstdio>
 the using  namespace STD;
 int A [ 10 ];
 int main () {
     int I, H, SUM, * P;    // declare variables 
    for (I = 0 ; I < 10 ; I ++ ) 
      Scanf ( " % D " , A & [I]);    // loop input 
    Scanf ( " % D " , & H);    // input itself height 
    H + = 30 ;   // plus stool height 
    SUM = 0 ;    // Apple can pick the total number 
    p A =;    //a is the array a first address 
    for (I = 0 ; I < 10 ; I ++ ) {
         IF (* P <= H)    // determines whether to pick 
          SUM ++;    // able to pick + 1'd 
        P ++;    // this p ++ is not a memory address at +1, but + sizeof (int) (to see him what type of pointer variable, if it is double plus sizeof (double)) 
    } 
    printf ( " % d " , SUM);    // output Total 
    return  0 ; 
}

We can see, p ++ refers to an integer after arrival. Thus be obtained: p-- before arrival is an integer, p = p + 3 is an integer of 3 to move backward, and the (p + 3) is the address of the third integer later.

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