思路：

题意描述不清，应该问最多有多少次碰撞。

参考了

实现：

1 #include 
     
       2 using namespace std; 3 typedef long long ll; 4 typedef pair
      
        pll; 5 int main() 6 { 7     int n; 8     ll a, b, x, p, q; 9     while (cin >> n >> a >> b)10     {11         map
       
        > mp;12         for (int i = 0; i < n; i++)13         { 14             cin >> x >> p >> q;15             ll tmp = a * p - q;16             pll k(p, q);17             if (!mp.count(tmp)) { mp[tmp] = map
        
         (); mp[tmp][k] = 0; }18             mp[tmp][k]++;19         }20         ll ans = 0;21         for (auto it: mp)22         {23             ll tot = 0;24             for (auto itr: it.second) tot += itr.second;25             for (auto itr: it.second) ans += itr.second * (tot - itr.second);26         }27         cout << ans << endl;28     }29     return 0;30 }