Competitive_Programming/Miscellaneous/meetinthemiddle.cpp at master · jonh14lk/Competitive_Programming · GitHub

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#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

template <class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define int long long int
#define pb push_back
#define pi pair<int, int>
#define pii pair<pi, int>
#define fir first
#define sec second
#define DEBUG 0
#define MAXN 1000001

int n, t;
vector<int> v;
vector<int> a;
vector<int> b;

void solve2(int i, int j, int k)
{
  if (i == j)
  {
    b.pb(k);
    return;
  }
  solve2(i + 1, j, k);
  solve2(i + 1, j, k + v[i]);
}
void solve(int i, int j, int k)
{
  if (i == j)
  {
    a.pb(k);
    return;
  }
  solve(i + 1, j, k);
  solve(i + 1, j, k + v[i]);
}
int upper(int l, int r, int x)
{
  while (l < r)
  {
    int mid = (l + r + 1) >> 1;
    (b[mid] <= x) ? l = mid : r = mid - 1;
  }
  return b[l];
}
int meetinthemiddle()
{
  solve(0, (n >> 1) + 1, 0);
  solve2((n >> 1) + 1, n, 0);
  sort(b.begin(), b.end());
  int ans = 0;
  for (auto const &i : a)
  {
    if (i > t)
      continue;
    ans = max(ans, i);
    int kappa = i + upper(0, b.size() - 1, t - i);
    if (kappa <= t)
      ans = max(ans, kappa);
  }
  return ans;
}
signed main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> t;
  v.resize(n);
  for (int i = 0; i < n; i++)
    cin >> v[i];
  cout << meetinthemiddle() << endl;
  return 0;
}