Nested class: how to access the member variable in enclosed class - c++

Question

The following code snippet aims to store all points in the member function mainFunc of enclosing class Solution in a priority_queue (i.e. pq), such that all points are in the order according to their distance to origin. However, the compiler reports an error:
error: invalid use of non-static data member 'Solution::ori'
Then I change the 3rd line of Point ori to static Point ori and change ori to Solution::ori in the function of distance(Point p), the link error occurs:
undefined reference to 'Solution::ori'
Could anyone help me on this? Thanks in advance!
/**
* Definition for a point.
* struct Point {
* int x;
* int y;
* Point() : x(0), y(0) {}
* Point(int a, int b) : x(a), y(b) {}
* };
*/
class Solution {
private:
Point ori;
class Comparator {
public:
// calculate the euclidean distance between p and ori
int distance(Point p) {
return pow(p.x-ori.x, 2) + pow(p.y-ori.y, 2);
}
// overload the comparator (), the nearest point to
// origin comes to the first
bool operator() (Point l, Point r) {
if (distance(l) > distance(r)) {
return true;
}
}
};
public:
/*
* #param points: a list of points
* #param origin: a point
*/
void mainFunc(vector<Point> points, Point origin) {
ori = origin;
priority_queue<Point, vector<Point>, Comparator> pq;
for (int i = 0; i < points.size(); i++) {
pq.push(points[i]);
}
}
};

Answer 1

You can modify your Comparator declaration to take a certain Point value in it's constructor:
class Solution {
private:
Point ori;
class Comparator {
public:
// Save the value in the functor class
Comparator(const Point& origin) : origin_(origin) {}
// calculate the euclidean distance between p and origin
int distance(Point p) {
return pow(p.x-origin_.x, 2) + pow(p.y-origin_.y, 2);
}
// overload the comparator (), the nearest point to
// origin comes to the first
bool operator() (Point l, Point r) {
if (distance(l) > distance(r)) {
return true;
}
}
private:
Point origin_;
};
public:
/*
* #param points: a list of points
* #param origin: a point
*/
void mainFunc(vector<Point> points, Point origin) {
ori = origin;
priority_queue<Point, vector<Point>> pq(Comparator(ori));
// ^^^^^^^^^^^^^^^
// Pass an instance of
// the functor class
for (int i = 0; i < points.size(); i++) {
pq.push(points[i]);
}
}
};