1 #include<iostream>
 2 #include<string>
 3 #include<cassert>
 4 using namespace std;
 5 
 6 class SmartPointer {
 7 public:
 8     int* ptr;
 9     int* count;
10 
11 public:
12 
13     SmartPointer(int* temp=nullptr):ptr(temp){
14         cout << "建構函式" << endl;
15         if
 
 (ptr) {
16             count = new int(1);
17         }
18         else {
19             count = new int(0);
20         }
21     }
22 
23 
24 
25     
26     SmartPointer(const SmartPointer& src) {
27         if (this != &src) {
28             ptr = src.ptr;
29             count = src.count;
 
30             (*count)++;
31         }
32         
33     }
34 
35     
36     SmartPointer& operator=(const SmartPointer& src) {
37         if (ptr == src.ptr) {
38             return *this;
39         }
40         if (ptr) {
41             (*count)--;
42             if ((*count) == 0) {
43                 delete
 
 ptr;
44                 delete count;
45             }
46         }
47         ptr = src.ptr;
48         count = src.count;
49         (*count)++;
50     }
51 
52     
53     int& operator*() {
54         assert(ptr != nullptr);
55         return *ptr;
56     }
57 
58     
59     int* operator->() {
60         assert(ptr != nullptr);
61         return ptr;
62     }
63 
64     ~SmartPointer() {
65         (*count)--;
66         if (*count == 0) {
67             delete count;
68             delete ptr;
69         }
70     }
71 
72     int use_count() const {
73         return *count;
74     }
75 
76 
77 };
78 
79 int main() 
80 {
81     SmartPointer sp(new int(10));
82     std::cout << sp.use_count() << std::endl;
83 
84     SmartPointer sp2(sp);
85     std::cout << sp.use_count() << std::endl;
86     std::cout << sp2.use_count() << std::endl;
87 
88     SmartPointer sp3(new int(20));
89     std::cout << sp3.use_count() << std::endl;
90 
91 
92     sp2 = sp3;
93     std::cout << sp.use_count() << std::endl;
94     std::cout << sp2.use_count() << std::endl;
95     std::cout << sp3.use_count() << std::endl;
96         //delete operator    
97 }