[Error] invalid use of non-static data member 'solve::a'

#include<bits/stdc++.h>
using namespace std;
#define ll long long
struct node{
	int x1,y1,x2,y2;
};
int n,m,k;
class solve{
	node a[100005];
	struct point{
		int y;
		bool flag;//0: zuo, 1: you
		bool operator <(const point& p) const{
			return (flag?a[y].y2:a[y].y1)>(p.flag?a[p.y].y2:a[p.y].y1);
		}
	};
}g1;
int main()
{
	return 0;
}