set有关的函数的用法（The SetStack Computer UVA - 12096）

#include<bits/stdc++.h>
using namespace std;
typedef set<int> Set;
map<Set,int> IDcache;
vector<Set> Setcache;
stack<int> s;
int ID(Set x)
{
	if(IDcache.count(x))	return IDcache[x];
	Setcache.push_back(x);
	return IDcache[x]=Setcache.size()-1;
}
int t,n;
int main()
{
	int i,j;
	string op;
	Set x1,x2,x;
	scanf("%d",&t);
	for(i=1;i<=t;i++)
	{
		scanf("%d",&n);
		for(j=1;j<=n;j++)
		{
			cin>>op;
			if(op[0]=='P')
				s.push(ID(Set()));
			else if(op[0]=='D')
				s.push(s.top());
			else
			{
				x1.clear();x2.clear();x.clear();
				x1=Setcache[s.top()];s.pop();
				x2=Setcache[s.top()];s.pop();
				//http://blog.csdn.net/zangker/article/details/22984803
				//http://blog.csdn.net/neo_2011/article/details/7366248
				//最后一个参数若使用x.begin()会产生编译错误assignment of read-only localtion.
				//但是如果x是vector则可以直接用x.begin()
				if(op[0]=='U')
					set_union(x1.begin(),x1.end(),x2.begin(),x2.end(),inserter(x,x.begin()));
				if(op[0]=='I')
					set_intersection(x1.begin(),x1.end(),x2.begin(),x2.end(),inserter(x,x.begin()));
				if(op[0]=='A')
				{
					x=x2;
					x.insert(ID(x1));
				}
				s.push(ID(x));
			}
			printf("%d\n",Setcache[s.top()].size());
		}
		printf("***\n");
	}
	return 0;
}

set_union的说明

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合并集合(set<...>)x1,x2，并放入新集合x

set_union(x1.begin(),x1.end(),x2.begin(),x2.end(),inserter(x,x.begin()));

合并数组x1,x2(要求原本有序)：

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int first[]={1,2,3,4,5};
	int second[]={3,4,5,6,7};
	int third[10]={0};
	set_union(first,first+5,second,second+5,third);
	//set_union(begin(first),end(first),begin(second),end(second),begin(third));//作用同上，begin()和end()是c++11新特性
	for(int i=0;i<10;i++)
		printf("%d ",third[i]);
}

#include<bits/stdc++.h>//没排序就像这样，输出奇怪的东西
using namespace std;
int main()
{
	int first[]={1,2,3,4,5};
	int second[]={7,4,6,5,4};
	int third[10]={0};
	set_union(first,first+5,second,second+5,third);
	for(int i=0;i<10;i++)
		printf("%d ",third[i]);
}

求集合x1,x2的交集，并放入新集合x

set_intersection(x1.begin(),x1.end(),x2.begin(),x2.end(),inserter(x,x.begin()));

（数组类似）