Running median

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;


typedef tree<int, null_type,greater_equal<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;

vector<int> Solution::solve(vector<int> &a) {
    vector<int> ans;
    ordered_set st;
    for(int x:a){
        st.insert(x);
        ans.push_back(*st.find_by_order(st.size()/2));
    }
    return ans;
}