UVa 496

　　题目大意：给你两个集合，判断两个集合的关系（不相交、相等、真子集和其他）。简单判断就可以了，不过STL的set没有交集、并集等操作有点让人觉得不方便...

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <set>
 4 using namespace std;
 5 
 6 set<int> intersection(const set<int> &a, const set<int> &b)
 7 {
 8     set<int>::iterator itA = a.begin(), itB = b.begin();
 9     set<int> c;
10     while (itA != a.end() && itB != b.end())
11     {
12         if (*itA == *itB)
13         {
14             c.insert(*itA);
15             itA++;
16             itB++;
17         }
18         else if (*itA < *itB)  itA++;
19         else if (*itA > *itB)  itB++;
20     }
21     return c;
22 }
23 
24 int main()
25 {
26 #ifdef LOCAL
27     freopen("in", "r", stdin);
28 #endif
29     int x;
30     while (scanf("%d", &x) != EOF)
31     {
32         set<int> A, B, C;
33         A.insert(x);
34         C.insert(x);
35         while (getchar() != '
')
36         {
37             scanf("%d", &x);
38             A.insert(x);
39             C.insert(x);
40         }
41         scanf("%d", &x);
42         B.insert(x);
43         C.insert(x);
44         while (getchar() != '
')
45         {
46             scanf("%d", &x);
47             B.insert(x);
48             C.insert(x);
49         }
50         if (A.size() + B.size() == C.size())  printf("A and B are disjoint
"); 
51         else if (A == B)  printf("A equals B
");
52         else
53         {
54             set<int> s = intersection(A, B);
55             if (A == s)  printf("A is a proper subset of B
");
56             else if (B == s)  printf("B is a proper subset of A
");
57             else  printf("I'm confused!
");
58         }
59     }
60     return 0;
61 }

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@2013-11-10 11:50:07

　前两天看C++ Primer的时候，看到标准库里有set_union(), set_intersection(), set_difference() 和 set_symmetirc_difference()函数，就重写了一下，提交后和上面那个代码时间一样，不过省了不少功夫哈，对c++还是不熟悉啊，还要多学习。

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <set>
 4 #include <algorithm>
 5 using namespace std;
 6 
 7 int main()
 8 {
 9 #ifdef LOCAL
10     freopen("in", "r", stdin);
11 #endif
12     int x;
13     while (scanf("%d", &x) != EOF)
14     {
15         set<int> A, B, C;
16         A.insert(x);
17         C.insert(x);
18         while (getchar() != '
')
19         {
20             scanf("%d", &x);
21             A.insert(x);
22             C.insert(x);
23         }
24         scanf("%d", &x);
25         B.insert(x);
26         C.insert(x);
27         while (getchar() != '
')
28         {
29             scanf("%d", &x);
30             B.insert(x);
31             C.insert(x);
32         }
33         if (A.size() + B.size() == C.size())  printf("A and B are disjoint
");
34         else if (A == B)  printf("A equals B
");
35         else
36         {
37             set<int> s;
38             set_intersection(A.begin(), A.end(), B.begin(), B.end(), inserter(s, s.begin()));
39             if (A == s)  printf("A is a proper subset of B
");
40             else if (B == s)  printf("B is a proper subset of A
");
41             else  printf("I'm confused!
");
42         }
43     }
44     return 0;
45 }

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