UVa 496 Simply Subsets (STL&set_intersection)

先介绍 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
          
           
using namespace std;

int a[100], b[100];
vector
           
             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; }