CF1072C Cram Time

思路：

首先二分找到使x * (x + 1) / 2 <= a + b最大的x，然后令p = min(a, b), q = max(a, b),按照x，x - 1, ..., 1的顺序选取数字把p填满，把剩下未选择的数字放到q中即可。

实现：

 #include <iostream>
 #include <set>
 #include <vector>
 using namespace std;

 typedef long long ll;

 inline bool check(ll x, ll a, ll b)
 {
     return x * (x + ) /  <= a + b;
 }

 int main()
 {
     ll a, b;
     while (cin >> a >> b)
     {
         ll l = , r = , ans = -;
         while (l <= r)
         {
             ll m = l + r >> ;
             if (check(m, a, b))
             {
                 l = m + ;
                 ans = m;
             }
             else
             {
                 r = m - ;
             }
         }
         set<int> st;
         int x = min(a, b);
         for (int i = ans; i >= ; i--)
         {
             if (i > x) continue;
             st.insert(i);
             x -= i;
         }
         set<int> st2;
         for (int i = ; i <= ans; i++)
         {
             if (!st.count(i)) st2.insert(i);
         }
         if (a > b) swap(st, st2);
         cout << st.size() << endl;
         for (auto it: st) cout << it << " ";
         cout << endl;
         cout << st2.size() << endl;
         for (auto it: st2) cout << it << " ";
         cout << endl;
     }
     return ;
 }