1 #include <iostream>
 2 using namespace std;
 3 
 4 namespace A{
 5     int a = 1;
 6 }
 7 
 8 namespace B{
 9     int b = 2;
10 }
11 
12 namespace C{
13     int c = 3;
14 }
15 
16 int main(){
17 
18     int a = 10;
19     int b = 20;
20     int c = 30;
21 
22     using namespace A;
23     using namespace B;
24     using namespace C;
25 
26     cout<<"a = "<<a<<endl;
27     cout<<"b = "<<b<<endl;
28     cout<<"c = "<<c<<endl;
29 
30     cout<<"a::a = "<<A::a<<endl;
31     cout<<"b::b = "<<B::b<<endl;
32     cout<<"c::c = "<<C::c<<endl;
33 
34     system("pause");
35     return 0;
36 }

1 a = 10
2 b = 20
3 c = 30
4 a::a = 1
5 b::b = 2
6 c::c = 3
7 请按任意键继续. . .

 1 namespace A{
 2     int a = 1;
 3 }
 4 
 5 namespace B{
 6     int b = 2;
 7 }
 8 
 9 namespace C{
10     int c = 3;
11     int b = 3;
12 }
13 
14 int main(){
15 
16     //int a = 10;
17     //int b = 20;
18     //int c = 30;
19 
20     using namespace A;
21     using namespace B;
22     using namespace C;
23 
24     cout<<"a = "<<a<<endl;
25     cout<<"b = "<<b<<endl;
26     cout<<"c = "<<c<<endl;