二维结构体vector CE是咋回事？

报错那行的代码

int xmn=x2[1].lower_bound(x2[1].begin(),x2[1].end(),1)-x2[1].begin()-1;

vector 与 node 的定义

struct node{
    int num;
    int id;
    bool operator<(const node &cmp)const{
        return num<cmp.num;
    }
    bool operator>(const node &cmp)const{
        return num>cmp.num;
    }
    bool operator==(const node &cmp)const{
        return num==cmp.num;
    }
};
vector<node>x1[N];
vector<node>y1[N];
vector<node>x2[N];
vector<node>y2[N];

报错信息

[Error] 'class std::vector<node>' has no member named 'lower_bound'

求条悬两关