Problem p03522 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#define dbg() cerr <<
#define name(x) (#x) << ": " << (x) << ' ' <<

using namespace std;

struct SegmTree {
  int n;
  vector<int> a, tree, lazy, where;
  SegmTree(const vector<int> a_)
      : n(a_.size()), a(a_), tree(4 * n), lazy(4 * n), where(4 * n) {
    Build(0, 0, n - 1);
  }
  void Recalc(int node) {
    if (tree[2 * node + 1] < tree[2 * node + 2]) {
      tree[node] = tree[2 * node + 1];
      where[node] = where[2 * node + 1];
    } else {
      tree[node] = tree[2 * node + 2];
      where[node] = where[2 * node + 2];
    }
  }
  void Build(int node, int left, int right) {
    if (left == right) {
      tree[node] = a[left];
      where[node] = left;
      return;
    }
    int mid = left + (right - left) / 2;
    Build(2 * node + 1, left, mid);
    Build(2 * node + 2, mid + 1, right);
    Recalc(node);
  }
  inline void Add(int node, int val) {
    tree[node] += val;
    lazy[node] += val;
  }
  inline void Propagate(int node) {
    if (lazy[node] == 0)
      return;
    Add(2 * node + 1, lazy[node]);
    Add(2 * node + 2, lazy[node]);
    lazy[node] = 0;
  }
  void Update(int node, int left, int right, int pos) {
    if (pos >= right) {
      Add(node, 1);
      return;
    }
    Propagate(node);
    int mid = left + (right - left) / 2;
    Update(2 * node + 1, left, mid, pos);
    if (mid < pos)
      Update(2 * node + 2, mid + 1, right, pos);
    Recalc(node);
  }
  pair<int, int> Query(int node, int left, int right, int pos) {
    if (left >= pos) {
      return make_pair(tree[node], where[node]);
    }
    Propagate(node);
    int mid = left + (right - left) / 2;
    pair<int, int> ret = {(int)2e9, -1};
    if (pos <= mid)
      ret = Query(2 * node + 1, left, mid, pos);
    ret = min(ret, Query(2 * node + 2, mid + 1, right, pos));
    return ret;
  }
  pair<int, int> Query(int pos) { return Query(0, 0, n - 1, pos); }
  void Update(int pos) {
    if (pos >= 0)
      Update(0, 0, n - 1, pos);
  }
};

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);

  int n;
  cin >> n;
  vector<int> a(n);
  for (int &x : a) {
    cin >> x;
  }
  auto b = a;
  sort(b.begin(), b.end());
  b.erase(unique(b.begin(), b.end()), b.end());
  SegmTree st(b);
  long long ans = 0;
  for (int i = 0; i < n; ++i) {
    int pos = find(b.begin(), b.end(), a[i]) - b.begin();
    pair<int, int> val = st.Query(pos);
    ans += val.first - a[i];
    st.Update(val.second - 1);
  }
  cout << ans << endl;

  cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
}

Fixed submission:
#include <bits/stdc++.h>
#define dbg() cerr <<
#define name(x) (#x) << ": " << (x) << ' ' <<

using namespace std;

struct SegmTree {
  int n;
  vector<int> a, tree, lazy, where;
  SegmTree(const vector<int> a_)
      : n(a_.size()), a(a_), tree(4 * n), lazy(4 * n), where(4 * n) {
    Build(0, 0, n - 1);
  }
  void Recalc(int node) {
    if (tree[2 * node + 1] < tree[2 * node + 2]) {
      tree[node] = tree[2 * node + 1];
      where[node] = where[2 * node + 1];
    } else {
      tree[node] = tree[2 * node + 2];
      where[node] = where[2 * node + 2];
    }
  }
  void Build(int node, int left, int right) {
    if (left == right) {
      tree[node] = a[left];
      where[node] = left;
      return;
    }
    int mid = left + (right - left) / 2;
    Build(2 * node + 1, left, mid);
    Build(2 * node + 2, mid + 1, right);
    Recalc(node);
  }
  inline void Add(int node, int val) {
    tree[node] += val;
    lazy[node] += val;
  }
  inline void Propagate(int node) {
    if (lazy[node] == 0)
      return;
    Add(2 * node + 1, lazy[node]);
    Add(2 * node + 2, lazy[node]);
    lazy[node] = 0;
  }
  void Update(int node, int left, int right, int pos) {
    if (pos >= right) {
      Add(node, 1);
      return;
    }
    Propagate(node);
    int mid = left + (right - left) / 2;
    Update(2 * node + 1, left, mid, pos);
    if (mid < pos)
      Update(2 * node + 2, mid + 1, right, pos);
    Recalc(node);
  }
  pair<int, int> Query(int node, int left, int right, int pos) {
    if (left >= pos) {
      return make_pair(tree[node], where[node]);
    }
    Propagate(node);
    int mid = left + (right - left) / 2;
    pair<int, int> ret = {(int)2e9, -1};
    if (pos <= mid)
      ret = Query(2 * node + 1, left, mid, pos);
    ret = min(ret, Query(2 * node + 2, mid + 1, right, pos));
    return ret;
  }
  pair<int, int> Query(int pos) { return Query(0, 0, n - 1, pos); }
  void Update(int pos) {
    if (pos >= 0)
      Update(0, 0, n - 1, pos);
  }
};

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);

  int n;
  cin >> n;
  vector<int> a(n);
  for (int &x : a) {
    cin >> x;
  }
  auto b = a;
  sort(b.begin(), b.end());
  b.erase(unique(b.begin(), b.end()), b.end());
  SegmTree st(b);
  long long ans = 0;
  for (int i = 0; i < n; ++i) {
    int pos = lower_bound(b.begin(), b.end(), a[i]) - b.begin();
    pair<int, int> val = st.Query(pos);
    ans += val.first - a[i];
    st.Update(val.second - 1);
  }
  cout << ans << endl;

  cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
}