结构体重载运算符

struct node{
    int a,b;
    node& operator + (node &xx)
    {
        a += xx.a;
        b += xx.b;
    }
};

struct node{
    int a,b;
    bool operator < (const node &xx)const
    {
        if(a==xx.a)
        {
            return b < xx.b;
        }
        else return a<xx.a;
    }
};