C中指针和数组的区别？-yiteyi-C++库

指针用于存储动态分配数组的地址，以及作为参数传递给函数的数组。在其他上下文中，数组和指针是两个不同的东西，请参阅以下程序来证明此语句的正确性。 sizeof算子的行为

null

C++

                         // 1st program to show that array and pointers are different                       
                         #include <iostream>                       
                         using                                     namespace                                     std;                       
           
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = { 10, 20, 30, 40, 50, 60 };                       
                                                 int                                     * ptr = arr;                       
           
                                                 // sizof(int) * (number of element in arr[]) is printed                       
                                                 cout <<                                     "Size of arr[] "                                     <<                                     sizeof                                     (arr) <<                                     ""                                     ;                       
           
                                                 // sizeof a pointer is printed which is same for all                       
                                                 // type of pointers (char *, void *, etc)                       
                                                 cout <<                                     "Size of ptr "                                     <<                                     sizeof                                     (ptr);                       
                                                 return                                     0;                       
                         }                       

C

                         // 1st program to show that array and pointers are different                       
                         #include <stdio.h>                       
           
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = { 10, 20, 30, 40, 50, 60 };                       
                                                 int                                     * ptr = arr;                       
           
                                                 // sizof(int) * (number of element in arr[]) is printed                       
                                                 printf                                     (                                     "Size of arr[] %ld"                                     ,                                     sizeof                                     (arr));                       
           
                                                 // sizeof a pointer is printed which is same for all                       
                                                 // type of pointers (char *, void *, etc)                       
                                                 printf                                     (                                     "Size of ptr %ld"                                     ,                                     sizeof                                     (ptr));                       
                                                 return                                     0;                       
                         }                       

输出

Size of arr[] 24Size of ptr 8

不允许将任何地址分配给数组变量。

C++

                         // IInd program to show that array                       
                         // and pointers are different                       
                         #include <iostream>                       
                         using                                     namespace                                     std;                       
           
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = {10, 20}, x = 10;                       
                                                 int                                     *ptr = &x;                                     // This is fine                       
                                                 arr = &x;                                     // Compiler Error                       
                                                 return                                     0;                       
                         }                       
           
                         // This code is contributed by Shubhamsingh10                       

C

                         // IInd program to show that array and pointers are different                       
                         #include <stdio.h>                       
           
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = {10, 20}, x = 10;                       
                                                 int                                     *ptr = &x;                                     // This is fine                       
                                                 arr = &x;                                     // Compiler Error                       
                                                 return                                     0;                       
                         }                       

输出：

 Compiler Error: incompatible types when assigning to               type 'int[2]' from type 'int *'

看到了吗以前的职位在这个话题上有更多的分歧。 虽然数组和指针是不同的东西，但数组的以下属性使它们看起来很相似。

数组名给出数组第一个元素的地址。

例如，考虑下面的程序。

C++

                         // 1st program to show that array and pointers are different                       
                         #include <iostream>                       
                         using                                     namespace                                     std;                       
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = { 10, 20, 30, 40, 50, 60 };                       
           
                                                 // Assigns address of array to ptr                       
                                                 int                                     * ptr = arr;                       
                                                 cout <<                                     "Value of first element is "                                     << *ptr;                       
                                                 return                                     0;                       
                         }                       

C

                         #include <stdio.h>                       
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = { 10, 20, 30, 40, 50, 60 };                       
                                                 // Assigns address of array to ptr                       
                                                 int                                     * ptr = arr;                       
                                                 printf                                     (                                     "Value of first element is %d"                                     , *ptr);                       
                                                 return                                     0;                       
                         }                       

输出

Value of first element is 10

使用指针算法访问数组成员。 编译器使用指针算法来访问数组元素。例如，像“arr[i]”这样的表达式被编译器视为*（arr+i）。这就是为什么像*（arr+i）这样的表达式适用于数组arr，像ptr[i]这样的表达式也适用于指针ptr。

C++

                         #include <iostream>                       
                         using                                     namespace                                     std;                       
           
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = { 10, 20, 30, 40, 50, 60 };                       
                                                 int                                     * ptr = arr;                       
                                                 cout <<                                     "arr[2] = "                                     << arr[2] <<                                     ""                                     ;                       
                                                 cout <<                                     "*(arr + 2) = "                                     << *(arr + 2) <<                                     ""                                     ;                       
                                                 cout <<                                     "ptr[2] = "                                     << ptr[2] <<                                     ""                                     ;                       
                                                 cout <<                                     "*(ptr + 2) = "                                     << *(ptr + 2) <<                                     ""                                     ;                       
                                                 return                                     0;                       
                         }                       

C

                         #include <stdio.h>                       
           
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = {10, 20, 30, 40, 50, 60};                       
                                                 int                                     *ptr = arr;                       
                                                 printf                                     (                                     "arr[2] = %d"                                     , arr[2]);                       
                                                 printf                                     (                                     "*(arr + 2) = %d"                                     , *(arr + 2));                       
                                                 printf                                     (                                     "ptr[2] = %d"                                     , ptr[2]);                       
                                                 printf                                     (                                     "*(ptr + 2) = %d"                                     , *(ptr + 2));                       
                                                 return                                     0;                       
                         }                       

输出

arr[2] = 30*(arr + 2) = 30ptr[2] = 30*(ptr + 2) = 30

数组参数始终作为指针传递，即使使用方括号也是如此。

C++

                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         int                                     fun(                                     int                                     ptr[])                       
                         {                       
                                                 int                                     x = 10;                       
                                   
                                                 // Size of a pointer is printed                       
                                                 cout <<                                     "sizeof(ptr) = "                       
                                                 << (                                     int                                     )                                     sizeof                                     (*ptr)                       
                                                 << endl;                       
           
                                                 // This allowed because ptr is a                       
                                                 // pointer, not array                       
                                                 ptr = &x;                       
           
                                                 cout <<                                     "*ptr =  "                                     << *ptr;                       
           
                                                 return                                     0;                       
                         }                       
           
                         // Driver code                       
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = { 10, 20, 30, 40, 50, 60 };                       
                                   
                                                 // Size of a array is printed                       
                                                 cout <<                                     "sizeof(arr) = "                       
                                                 << (                                     int                                     )                                     sizeof                                     (arr)                       
                                                 << endl;                       
                                   
                                                 fun(arr);                       
                                   
                                                 return                                     0;                       
                         }                       
           
                         // This code is contributed by shivanisinghss2110                       

C

                         #include <stdio.h>                       
           
                         int                                     fun(                                     int                                     ptr[])                       
                         {                       
                                                 int                                     x = 10;                       
           
                                                 // size of a pointer is printed                       
                                                 printf                                     (                                     "sizeof(ptr) = %d"                                     , (                                     int                                     )                                     sizeof                                     (*ptr));                       
           
                                                 // This allowed because ptr is a pointer, not array                       
                                                 ptr = &x;                       
           
                                                 printf                                     (                                     "*ptr = %d "                                     , *ptr);                       
           
                                                 return                                     0;                       
                         }                       
           
                         // Driver code                       
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = { 10, 20, 30, 40, 50, 60 };                       
                                   
                                                 // size of a array is printed                       
                                                 printf                                     (                                     "sizeof(arr) = %d"                                     , (                                     int                                     )                                     sizeof                                     (arr));                       
                                                 fun(arr);                       
                                                 return                                     0;                       
                         }                       

输出

sizeof(arr) = 24sizeof(ptr) = 4*ptr = 10

请参考 C语言中的指针与数组更多细节。

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