题目

代码（巨复杂，跑了我十几分钟）

#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-6;
const int N = 18e6;
#define x first
#define y second
typedef pair<int, int> PII;
int line;
PII p1[N];
PII p2[N];
vector<PII> points;double cal(PII a, PII b)
{return sqrt(1.0 * (a.x - b.x) * (a.x - b.x) + 1.0 * (a.y - b.y) * (a.y - b.y));
}
bool at(int i, PII p)
{PII a = p1[i], b = p2[i];double dis[3];dis[0] = cal(p, a);dis[1] = cal(p, b);dis[2] = cal(a, b);sort(dis, dis + 3);return fabs(dis[0] + dis[1] - dis[2]) < eps;
}
bool check(PII a, PII b)
{for (int i = 1; i <= line; i++){if (at(i, a) && at(i, b))return false;}return true;
}
int main()
{for (int x = 0; x < 20; x++){for (int y = 0; y < 21; y++){points.push_back({x, y});}}for (auto a : points){for (auto b : points){if (a.x != b.x || a.y != b.y){if (check(a, b)){line++;p1[line] = a;p2[line] = b;}}}}cout << line;return 0;
}