CF962D Merge Equals

思路：

不必每次都找最小的值进行合并，从前往后扫一遍的过程中能合并就一直合并。

实现：

 #include <bits/stdc++.h>
 using namespace std;
 typedef long long ll;
 const int MAXN = ;
 ll a[MAXN];
 int main()
 {
     int n;
     while (cin >> n)
     {
         map<ll, int> mp;
         for (int i = ; i < n; i++)
         {
             cin >> a[i];
             if (mp.count(a[i]))
             {
                 while (mp.count(a[i]))
                 {
                     a[mp[a[i]]] = -;
                     mp.erase(a[i]);
                     a[i] <<= ;
                 }
             }
             mp[a[i]] = i;
         }
         vector<ll> v;
         for (int i = ; i < n; i++)
         {
             if (a[i] != -) v.push_back(a[i]);
         }
         cout << v.size() << endl;
         for (int i = ; i < v.size(); i++) cout << v[i] << " ";
         cout << endl;
     }
     return ;
 }