UVa 496 - Simply Subsets

　　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...

 #include <cstdio>
 #include <iostream>
 #include <set>
 using namespace std;

 set<int> intersection(const set<int> &a, const set<int> &b)
 {
     set<int>::iterator itA = a.begin(), itB = b.begin();
     set<int> c;
     while (itA != a.end() && itB != b.end())
     {
         if (*itA == *itB)
         {
             c.insert(*itA);
             itA++;
             itB++;
         }
         else if (*itA < *itB)  itA++;
         else if (*itA > *itB)  itB++;
     }
     return c;
 }

 int main()
 {
 #ifdef LOCAL
     freopen("in", "r", stdin);
 #endif
     int x;
     while (scanf("%d", &x) != EOF)
     {
         set<int> A, B, C;
         A.insert(x);
         C.insert(x);
         while (getchar() != '\n')
         {
             scanf("%d", &x);
             A.insert(x);
             C.insert(x);
         }
         scanf("%d", &x);
         B.insert(x);
         C.insert(x);
         while (getchar() != '\n')
         {
             scanf("%d", &x);
             B.insert(x);
             C.insert(x);
         }
         if (A.size() + B.size() == C.size())  printf("A and B are disjoint\n");
         else if (A == B)  printf("A equals B\n");
         else
         {
             set<int> s = intersection(A, B);
             if (A == s)  printf("A is a proper subset of B\n");
             else if (B == s)  printf("B is a proper subset of A\n");
             else  printf("I'm confused!\n");
         }
     }
     return ;
 }

　

---

@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。

 #include <cstdio>
 #include <iostream>
 #include <set>
 #include <algorithm>
 using namespace std;

 int main()
 {
 #ifdef LOCAL
     freopen("in", "r", stdin);
 #endif
     int x;
     while (scanf("%d", &x) != EOF)
     {
         set<int> A, B, C;
         A.insert(x);
         C.insert(x);
         while (getchar() != '\n')
         {
             scanf("%d", &x);
             A.insert(x);
             C.insert(x);
         }
         scanf("%d", &x);
         B.insert(x);
         C.insert(x);
         while (getchar() != '\n')
         {
             scanf("%d", &x);
             B.insert(x);
             C.insert(x);
         }
         if (A.size() + B.size() == C.size())  printf("A and B are disjoint\n");
         else if (A == B)  printf("A equals B\n");
         else
         {
             set<int> s;
             set_intersection(A.begin(), A.end(), B.begin(), B.end(), inserter(s, s.begin()));
             if (A == s)  printf("A is a proper subset of B\n");
             else if (B == s)  printf("B is a proper subset of A\n");
             else  printf("I'm confused!\n");
         }
     }
     return ;
 }