UVa 496 Simply Subsets (STL&set_intersection)

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http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=437

先介绍<algorithm>头文件中与集合运算有关的4个函数：

set_union: Union of two sorted ranges (并集：A∪B)

set_intersection: Intersection of two sorted ranges (交集：A∩B)

set_difference: Difference of two sorted ranges (差集：A-B)

set_symmetric_difference: Symmetric difference of two sorted ranges (对称差集：A△B)

很明显，这里要判断两个集合的关系，使用交集来判断就行了。

使用方法：

set_intersection(a, a + n, b, b + m, v.begin());

这里v是动态数组，用于保存交运算结果。（其他函数的使用方法均与之类似）

该函数的返回值减去v.begin()就是集合的大小。

完整代码：

/*0.016s*/#include<bits/stdc++.h>using namespace std;int a[100], b[100];vector<int> v(100);///初始化空间是必须的int main(){int n, m, cnt, diff;char ch;while (~scanf("%d%c", &a[0], &ch)){for (n = 1; ch != 10; ++n)scanf("%d%c", &a[n], &ch);cnt = scanf("%d%c", &b[0], &ch);for (m = 1; ch != 10 && cnt == 2; ++m)cnt = scanf("%d%c", &b[m], &ch);sort(a, a + n);sort(b, b + m);diff = set_intersection(a, a + n, b, b + m, v.begin()) - v.begin();if (diff == min(n, m)){if (n < m) puts("A is a proper subset of B");else if (n > m) puts("B is a proper subset of A");else puts("A equals B");}else if (diff) puts("I'm confused!");else puts("A and B are disjoint");}return 0;}