// 举例如下:    int a[] = {1,2,3,4,5,6,7,8,1,2};    int nSize = sizeof(a)/sizeof(a[0]);    using namespace std;    set<int> sint;    for(int i=0; i<nSize; ++i)    {        pair<set<int>::iterator,bool> result = sint.insert(i);        if(result.second == false) // 插入的值重复,返回false        {            // do something        }    }