迭代法括号问题leecode21

1.终止程序条件(if)

2.迭代每一层内容(for , if )

#include <QCoreApplication>
#include <QDebug>
#include <QVector>
#include <QString>

QVector<QString> vec ;

void back(QString str ,int n , int left_t ,int right_t)
{
    if (left_t == n && right_t == n )
    {
        vec.push_back(str) ;
        return ;
    }

    if (left_t < right_t)
    {
        return ;
    }

    if (left_t < n )
    {
        str += '(' ;
        back(str,n,left_t+1,right_t) ;
        str = str.left(str.size()-1) ;
    }

    if (right_t < n)
    {
        str += ')' ;
        back(str,n,left_t,right_t +1);
        str = str.left(str.size()-1) ;
    }

}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    int t=3 ;
    QString str = "" ;

    back(str,3,0,0);

    for (auto c : vec)
    {
        qDebug() << c ;
    }



    return a.exec();
}