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...

#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() != '
')
        {
            scanf("%d", &x);
            A.insert(x);
            C.insert(x);
        }
        scanf("%d", &x);
        B.insert(x);
        C.insert(x);
        while (getchar() != '
')
        {
            scanf("%d", &x);
            B.insert(x);
            C.insert(x);
        }
        if (A.size() + B.size() == C.size())  printf("A and B are disjoint
"); 
        else if (A == B)  printf("A equals B
");
        else
        {
            set<int> s = intersection(A, B);
            if (A == s)  printf("A is a proper subset of B
");
            else if (B == s)  printf("B is a proper subset of A
");
            else  printf("I'm confused!
");
        }
    }
    return 0;
}

 　

---

@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() != '
')
        {
            scanf("%d", &x);
            A.insert(x);
            C.insert(x);
        }
        scanf("%d", &x);
        B.insert(x);
        C.insert(x);
        while (getchar() != '
')
        {
            scanf("%d", &x);
            B.insert(x);
            C.insert(x);
        }
        if (A.size() + B.size() == C.size())  printf("A and B are disjoint
");
        else if (A == B)  printf("A equals B
");
        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
");
            else if (B == s)  printf("B is a proper subset of A
");
            else  printf("I'm confused!
");
        }
    }
    return 0;
}