La matriu i els punters estan estretament relacionats entre si. En C++, el nom d'una matriu es considera com un punter, és a dir, el nom d'una matriu conté l'adreça d'un element. C++ considera el nom de la matriu com l'adreça del primer element. Per exemple, si creem una matriu, és a dir, marques que contenen els 20 valors de tipus enter, aleshores les marques contindran l'adreça del primer element, és a dir, marks[0]. Per tant, podem dir que el nom de la matriu (marks) és un punter que conté l'adreça del primer element d'una matriu.
convenció de nomenclatura de java
Entenem aquest escenari a través d'un exemple.
#include using namespace std; int main() { int *ptr; // integer pointer declaration int marks[10]; // marks array declaration std::cout << 'Enter the elements of an array :' << std::endl; for(int i=0;i>marks[i]; } ptr=marks; // both marks and ptr pointing to the same element.. std::cout << 'The value of *ptr is :' <<*ptr<< std::endl; std::cout << 'the value of *marks is :' <<*marks<<std::endl; } < pre> <p>In the above code, we declare an integer pointer and an array of integer type. We assign the address of marks to the ptr by using the statement ptr=marks; it means that both the variables 'marks' and 'ptr' point to the same element, i.e., marks[0]. When we try to print the values of *ptr and *marks, then it comes out to be same. Hence, it is proved that the array name stores the address of the first element of an array.</p> <p> <strong>Output</strong> </p> <img src="//techcodeview.com/img/c-tutorial/74/c-array-pointers.webp" alt="C++ Array of Pointers"> <h3>Array of Pointers</h3> <p>An array of pointers is an array that consists of variables of pointer type, which means that the variable is a pointer addressing to some other element. Suppose we create an array of pointer holding 5 integer pointers; then its declaration would look like:</p> <pre> int *ptr[5]; // array of 5 integer pointer. </pre> <p>In the above declaration, we declare an array of pointer named as ptr, and it allocates 5 integer pointers in memory.</p> <p>The element of an array of a pointer can also be initialized by assigning the address of some other element. Let's observe this case through an example.</p> <pre> int a; // variable declaration. ptr[2] = &a; </pre> <p>In the above code, we are assigning the address of 'a' variable to the third element of an array 'ptr'.</p> <p>We can also retrieve the value of 'a' be dereferencing the pointer.</p> <pre> *ptr[2]; </pre> <p> <strong>Let's understand through an example.</strong> </p> <pre> #include using namespace std; int main() { int ptr1[5]; // integer array declaration int *ptr2[5]; // integer array of pointer declaration std::cout << 'Enter five numbers :' << std::endl; for(int i=0;i> ptr1[i]; } for(int i=0;i<5;i++) { ptr2[i]="&ptr1[i];" } printing the values of ptr1 array std::cout << 'the are' std::endl; for(int i="0;i<5;i++)" *ptr2[i] < pre> <p>In the above code, we declare an array of integer type and an array of integer pointers. We have defined the 'for' loop, which iterates through the elements of an array 'ptr1', and on each iteration, the address of element of ptr1 at index 'i' gets stored in the ptr2 at index 'i'.</p> <p> <strong>Output</strong> </p> <img src="//techcodeview.com/img/c-tutorial/74/c-array-pointers-2.webp" alt="C++ Array of Pointers"> <p>Till now, we have learnt the array of pointers to an integer. Now, we will see how to create the array of pointers to strings.</p> <h3>Array of Pointer to Strings</h3> <p>An array of pointer to strings is an array of character pointers that holds the address of the first character of a string or we can say the base address of a string.</p> <p>The following are the differences between an array of pointers to string and two-dimensional array of characters:</p> <ul> <li>An array of pointers to string is more efficient than the two-dimensional array of characters in case of memory consumption because an array of pointer to strings consumes less memory than the two-dimensional array of characters to store the strings.</li> <li>In an array of pointers, the manipulation of strings is comparatively easier than in the case of 2d array. We can also easily change the position of the strings by using the pointers.</li> </ul> <p>Let's see how to declare the array of pointers to string.</p> <p>First, we declare the array of pointer to string:</p> <pre> char *names[5] = {'john', 'Peter', 'Marco', 'Devin', 'Ronan'}; </pre> <p>In the above code, we declared an array of pointer names as 'names' of size 5. In the above case, we have done the initialization at the time of declaration, so we do not need to mention the size of the array of a pointer. The above code can be re-written as:</p> <pre> char *names[ ] = {'john', 'Peter', 'Marco', 'Devin', 'Ronan'}; </pre> <p>In the above case, each element of the 'names' array is a string literal, and each string literal would hold the base address of the first character of a string. For example, names[0] contains the base address of 'john', names[1] contains the base address of 'Peter', and so on. It is not guaranteed that all the string literals will be stored in the contiguous memory location, but the characters of a string literal are stored in a contiguous memory location.</p> <p> <strong>Let's create a simple example.</strong> </p> <pre> #include using namespace std; int main() { char *names[5] = {'john', 'Peter', 'Marco', 'Devin', 'Ronan'}; for(int i=0;i<5;i++) { std::cout << names[i] std::endl; } return 0; < pre> <p>In the above code, we have declared an array of char pointer holding 5 string literals, and the first character of each string is holding the base address of the string.</p> <p> <strong>Output</strong> </p> <img src="//techcodeview.com/img/c-tutorial/74/c-array-pointers-3.webp" alt="C++ Array of Pointers"> <hr></5;i++)></pre></5;i++)></pre></*ptr<<> A la declaració anterior, declarem una matriu de punters anomenada ptr i assigna 5 punters enters a la memòria.
L'element d'una matriu d'un punter també es pot inicialitzar assignant l'adreça d'algun altre element. Observem aquest cas a través d'un exemple.
int a; // variable declaration. ptr[2] = &a;
Al codi anterior, estem assignant l'adreça de la variable 'a' al tercer element d'una matriu 'ptr'.
També podem recuperar el valor de 'a' desreferenciant el punter.
classe de bombolles java
*ptr[2];
Entenem-ho a través d'un exemple.
commutador java
#include using namespace std; int main() { int ptr1[5]; // integer array declaration int *ptr2[5]; // integer array of pointer declaration std::cout << 'Enter five numbers :' << std::endl; for(int i=0;i> ptr1[i]; } for(int i=0;i<5;i++) { ptr2[i]="&ptr1[i];" } printing the values of ptr1 array std::cout << \'the are\' std::endl; for(int i="0;i<5;i++)" *ptr2[i] < pre> <p>In the above code, we declare an array of integer type and an array of integer pointers. We have defined the 'for' loop, which iterates through the elements of an array 'ptr1', and on each iteration, the address of element of ptr1 at index 'i' gets stored in the ptr2 at index 'i'.</p> <p> <strong>Output</strong> </p> <img src="//techcodeview.com/img/c-tutorial/74/c-array-pointers-2.webp" alt="C++ Array of Pointers"> <p>Till now, we have learnt the array of pointers to an integer. Now, we will see how to create the array of pointers to strings.</p> <h3>Array of Pointer to Strings</h3> <p>An array of pointer to strings is an array of character pointers that holds the address of the first character of a string or we can say the base address of a string.</p> <p>The following are the differences between an array of pointers to string and two-dimensional array of characters:</p> <ul> <li>An array of pointers to string is more efficient than the two-dimensional array of characters in case of memory consumption because an array of pointer to strings consumes less memory than the two-dimensional array of characters to store the strings.</li> <li>In an array of pointers, the manipulation of strings is comparatively easier than in the case of 2d array. We can also easily change the position of the strings by using the pointers.</li> </ul> <p>Let's see how to declare the array of pointers to string.</p> <p>First, we declare the array of pointer to string:</p> <pre> char *names[5] = {'john', 'Peter', 'Marco', 'Devin', 'Ronan'}; </pre> <p>In the above code, we declared an array of pointer names as 'names' of size 5. In the above case, we have done the initialization at the time of declaration, so we do not need to mention the size of the array of a pointer. The above code can be re-written as:</p> <pre> char *names[ ] = {'john', 'Peter', 'Marco', 'Devin', 'Ronan'}; </pre> <p>In the above case, each element of the 'names' array is a string literal, and each string literal would hold the base address of the first character of a string. For example, names[0] contains the base address of 'john', names[1] contains the base address of 'Peter', and so on. It is not guaranteed that all the string literals will be stored in the contiguous memory location, but the characters of a string literal are stored in a contiguous memory location.</p> <p> <strong>Let's create a simple example.</strong> </p> <pre> #include using namespace std; int main() { char *names[5] = {'john', 'Peter', 'Marco', 'Devin', 'Ronan'}; for(int i=0;i<5;i++) { std::cout << names[i] std::endl; } return 0; < pre> <p>In the above code, we have declared an array of char pointer holding 5 string literals, and the first character of each string is holding the base address of the string.</p> <p> <strong>Output</strong> </p> <img src="//techcodeview.com/img/c-tutorial/74/c-array-pointers-3.webp" alt="C++ Array of Pointers"> <hr></5;i++)></pre></5;i++)> En el codi anterior, vam declarar una matriu de noms de punter com a 'noms' de mida 5. En el cas anterior, hem fet la inicialització en el moment de la declaració, de manera que no cal esmentar la mida de la matriu d'un punter. El codi anterior es pot tornar a escriure com:
char *names[ ] = {'john', 'Peter', 'Marco', 'Devin', 'Ronan'}; En el cas anterior, cada element de la matriu 'noms' és un literal de cadena, i cada literal de cadena conté l'adreça base del primer caràcter d'una cadena. Per exemple, names[0] conté l'adreça base de 'john', names[1] conté l'adreça base de 'Peter', i així successivament. No es garanteix que tots els literals de cadena s'emmagatzemen a la ubicació de memòria contigua, però els caràcters d'un literal de cadena s'emmagatzemen en una ubicació de memòria contigua.
Creem un exemple senzill.
#include using namespace std; int main() { char *names[5] = {'john', 'Peter', 'Marco', 'Devin', 'Ronan'}; for(int i=0;i<5;i++) { std::cout << names[i] std::endl; } return 0; < pre> <p>In the above code, we have declared an array of char pointer holding 5 string literals, and the first character of each string is holding the base address of the string.</p> <p> <strong>Output</strong> </p> <img src="//techcodeview.com/img/c-tutorial/74/c-array-pointers-3.webp" alt="C++ Array of Pointers"> <hr></5;i++)>