Codeforces. 1336B Xenia and Colorful Gems

1.Problem
https://codeforces.com/contest/1336/problem/B

2.Idea
Assuming x <= y <=z.
Enumerating middle value, and find smallest and biggest value by binary_search.

3.Source

 int nr, ng, nb;  
 ll ans = 1LL << 60;  
 ll calc(ll x, ll y, ll z)  
 {  
      return (x - y)*(x - y) + (y - z)*(y - z) + (x - z)*(x - z);  
 }  
 void solve(vector<int> a, vector<int> b, vector<int> c) {  
      for (auto x : a) {  
           auto y = lower_bound(b.begin(), b.end(), x);  
           auto z = upper_bound(c.begin(), c.end(), x);  
           if (y == b.end() || z == c.begin()) { continue; }  
           z--;   
           ans = min(ans, calc(x, *y, *z));  
      }  
 }  
 int main()  
 {  
      int t; cin >> t;  
      while (t--) {  
           ans = 1LL << 62;  
           cin >> nr >> ng >> nb;  
           vector<int> r(nr), g(ng), b(nb);  
           for (int i = 0; i < nr; i++) {  
                cin >> r[i];  
           }  
           for (int i = 0; i < ng; i++) {  
                cin >> g[i];  
           }  
           for (int i = 0; i < nb; i++) {  
                cin >> b[i];  
           }  
           sort(r.begin(), r.end());  
           sort(g.begin(), g.end());  
           sort(b.begin(), b.end());  
           solve(r, g, b);  
           solve(r, b, g);  
           solve(g, r, b);  
           solve(g, b, r);  
           solve(b, g, r);  
           solve(b, r, g);  
           cout << ans << endl;  
      }  
      return 0;  
 }