QSet的有关问题

#include <QtCore>struct node{    int cx, cy;    bool operator < (const node &b) const     {        return cx < b.cx;    }};int main(int argc, char *argv[]){    QCoreApplication app(argc, argv);    QSet<node> ss;    QSet<node>::iterator iter;    node temp;    int i, j;    for(i=0,j=100;i<101;i++,j--)    {        temp.cx = i;        temp.cy = j;        ss.insert(temp);    }    for(iter=ss.begin();iter!=ss.end();++iter)        qDebug() << iter->cx << "  " << iter->cy;    return 0;}