为什么输出10？？？

[sjyzhxw]

int main()
{
	list<string> roster1,roster2;
	fill_n(back_inserter(roster1),10,"s");
	fill_n(back_inserter(roster2),5,"2");
	fill_n(back_inserter(roster2),5,"s");
	size_t cnt=0;
	list<string>::iterator it=roster1.begin();
	while((it=find_first_of(it,roster1.end(),roster2.begin(),roster2.end()))!=roster1.end())
	{
		++cnt;
		++it;
	}
	cout<<"found "<<cnt<<" names on both rosters."<<endl;
}

roster1里10个s，roster2里5个2,5个s
然后这个程序是寻找两个list里有多少相同元素的。
应该是5啊。

[sjyzhxw]

int main()
{
vector<string> roster1,roster2;
fill_n(back_inserter(roster1),5,"s");
fill_n(back_inserter(roster1),5,"2");
fill_n(back_inserter(roster2),10,"s");
size_t cnt=0;
vector<string>::iterator it=roster1.begin();
while((it=find_first_of(it,roster1.end(),roster2.begin(),roster2.end()))!=roster1.end())
{
++cnt;
++it;
}
cout<<"found "<<cnt<<" names on both rosters."<<endl;
}

换顺序就不同了？

[未注销]

那是因为你it只是其中一个容器的迭代器，只是它增加了，另外一个没有增加啊。