C/C++ 指针难题?
cc++server side programmingprogramming
假设我们有一个大小为 4 字节的整数变量，另一个指针变量的大小为 8 字节。那么下面的输出是什么?
示例
#include<iostream>
using namespace std;
main() {
int a[4][5][6];
int x = 0;
int* a1 = &x;
int** a2 = &a1;
int*** a3 = &a2;
cout << sizeof(a) << " " << sizeof(a1) << " " << sizeof(a2) << " " << sizeof(a3) << endl;
cout << (char*)(&a1 + 1) - (char*)&a1 << " ";
cout << (char*)(&a2 + 1) - (char*)&a2 << " ";
cout << (char*)(&a3 + 1) - (char*)&a3 << " ";
cout << (char*)(&a + 1) - (char*)&a << endl;
cout << (char*)(a1 + 1) - (char*)a1 << " ";
cout << (char*)(a2 + 1) - (char*)a2 << " ";
cout << (char*)(a3 + 1) - (char*)a3 << " ";
cout << (char*)(a + 1) - (char*)a << endl;
cout << (char*)(&a[0][0][0] + 1) - (char*)&a[0][0][0] << " ";
cout << (char*)(&a[0][0] + 1) - (char*)&a[0][0] << " ";
cout << (char*)(&a[0] + 1) - (char*)&a[0] << " ";
cout << (char*)(&a + 1) - (char*)&a << endl;
cout << (a[0][0][0] + 1) - a[0][0][0] << " ";
cout << (char*)(a[0][0] + 1) - (char*)a[0][0] << " ";
cout << (char*)(a[0] + 1) - (char*)a[0] << " ";
cout << (char*)(a + 1) - (char*)a;
}
要解决这个问题，我们可以遵循以下一些要点 −
整数大小为 4 字节(32 位)，指针大小为 8 字节。如果我们用指针加 1，它将指向下一个直接类型。
&a1 是 int** 类型，&a2 是 int*** 类型，&a3 是 int**** 类型。这里所有都指向指针。如果我们加 1，我们将添加 8 字节。
a[0][0][0] 是一个整数，&a[0][0][0] 是 int*，a[0][0] 是 int*，&a[0][0] 是 int(*)[6] 类型，依此类推。因此 &a 的类型为 int(*)[4][5][6]。
输出
480 8 8 8 8 8 8 480 4 8 8 120 4 24 120 480 1 4 24 120
