(7.3)--7.3pointerandarray.pdf

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1、Pointer and ArrayPointer and Array7.3After an array is defined,the system will allocate memory space with addresses for it.Pointer and Array7.3Givenint*p1;p1=a;Exampleint a4;After the array is defined,the system will allocate memory space with addresses for it,as shown in the figure below.Pointer an

2、d Array7.3Exampleint b22;After defining a two-dimensional array,the system will also allocate memory space for it.The elements in the two-dimensional array are stored in memory in a row-by-row manner,as shown in the following figure.Givenint*p2;p2=&b00;Pointer and Array7.3Assuming that p is a pointe

3、r and n is a positive integer,then p+n:the address of the n-th data after the address pointed to by p.p-n:the address of the n-th data before the address pointed to by p.Pointer ArithmeticPointer and Array7.3int main()int a=1,2,3,4,b22=5,6,7,8;int*p1=&a0,*p2=&b00;int i,j;for(i=0;i4;i+)cout“The start

4、ing address of ai“isp1+i,the data stored in it is*(p1+i)endl;for(i=0;i2;i+)for(j=0;j2;j+)cout“The starting address of bijisp2+i*2+j,the data stored in it is*(p2+i*2+j)endl;return 0;E.g.1Use pointer variables to manipulate arrays.Pointer and Array7.3In the above program,pointer variables p1 and p2 po

5、int to element a0 and element b00.p1+I and p2+i*2+j point to the starting addresses of element ai and bij.Pointer and Array7.3The differences between array names and pointer variablesint a4;int*p1=a;/OR int*p1=&a0;The array name a is a pointer constant,whose value is the starting address of the arra

6、y and cannot be changed.Assignment operations to the pointer constant a are wrong,such as a=a+1 or a=&ai”.The memory address stored in the pointer variable p1 can be changed.Assignment operations to the pointer variable p1 are correct,such as“p1=p1+1”or“p1=&ai Pointer and Array7.3The following forms

7、 are equivalentint a4;int*p1=a;/OR int*p1=&a0;*(p1+i)（or*(a+i)）can be written p1i（or ai）p1+i（or a+i）can be written&p1i（or&ai）Pointer and Array7.3Pointer constant to a rowThe array name of the two-dimensional array is a pointer constant pointing to the first row,and the array name represents the star

8、ting address of the two-dimensional array.int b22;b is equivalent to&b0,and b0 can be regarded as a one-dimensional array composed of 2 elements,that is,b0 is of type int2.Therefore,b+1 will skip an int2 and point to b1.Pointer and Array7.3In C+,the starting address of a two-dimensional array can be

9、 saved using a pointer variable that points to a row,and then the variable can be used to manipulate the two-dimensional array.The definition syntax is(*);Among them,refers to the number of elements of each row in the two-dimensional array(i.e.the number of columns).Pointer and Array7.3int main()int b22=5,6,7,8;int(*p)2;int i,j;p=b;for(i=0;i2;i+)for(j=0;j2;j+)coutbij=pijendl;return 0;E.g.2Use the pointer variable that points to a row to manipulate two-dimensional arrays.