Problem p00360 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
typedef pair<int, int> P;

#ifndef MAX
#define MAX 400000
#endif

// Range Update Query+Range Minimum Query
template <class T> class RUQ_RMQ {
public:
  int n;
  T dat[MAX], lazy[MAX], DEFAULT;
  bool (*cmp)(T, T);
  void init(
      int n_, bool (*c)(T, T) = [](int a, int b) { return a < b; },
      T d = INT_MAX) {
    cmp = c;
    DEFAULT = d;
    n = 1;
    while (n < n_)
      n <<= 1;
    for (int i = 0; i < 2 * n - 1; i++) {
      dat[i] = lazy[i] = DEFAULT;
    }
  }
  inline void push(int k) {
    if (lazy[k] == DEFAULT)
      return;
    dat[k] = lazy[k];
    if (k < n - 1) {
      lazy[k * 2 + 1] = lazy[k];
      lazy[k * 2 + 2] = lazy[k];
    }
    lazy[k] = DEFAULT;
  }
  inline void update_node(int k) {
    if (cmp(dat[k * 2 + 1], dat[k * 2 + 2]))
      dat[k] = dat[k * 2 + 1];
    else
      dat[k] = dat[k * 2 + 2];
  }
  inline void update(int a, int b, T x, int k, int l, int r) {
    push(k);
    if (r <= a || b <= l)
      return;
    if (a <= l && r <= b) {
      lazy[k] = x;
      push(k);
      return;
    }
    update(a, b, x, k * 2 + 1, l, (l + r) / 2);
    update(a, b, x, k * 2 + 2, (l + r) / 2, r);
    update_node(k);
  }
  inline T query(int a, int b, int k, int l, int r) {
    push(k);
    if (r <= a || b <= l)
      return DEFAULT;
    if (a <= l && r <= b)
      return dat[k];
    T lb = query(a, b, k * 2 + 1, l, (l + r) / 2);
    T rb = query(a, b, k * 2 + 2, (l + r) / 2, r);
    update_node(k);
    if (cmp(lb, rb))
      return lb;
    return rb;
  }
  inline void update(int a, int b, T x) { update(a, b, x, 0, 0, n); }
  inline void update(int a, T x) { update(a, a + 1, x); }
  inline T query(int a, int b) { return query(a, b, 0, 0, n); }
  inline T query(int a) { return query(a, a + 1); }
};

int bit[300000];
void add(int k, int x) {
  k++;
  while (k < 300000) {
    bit[k] += x;
    k += k & -k;
  }
}
int sum(int k) {
  k++;
  int ans = 0;
  while (k) {
    ans += bit[k];
    k -= k & -k;
  }
  return ans;
}
RUQ_RMQ<P> tree;
int main() {
  string s;
  int k;
  cin >> s >> k;
  rep(i, s.size() - 1) add(i + 1, 1);
  tree.init(
      s.size(), [](P a, P b) { return a < b; }, P(INT_MAX, INT_MAX));
  rep(i, s.size()) tree.update(i, P(s[i], i));
  string ans;
  int a = k;
  rep(i, s.size()) {
    int l = 1, r = s.size();
    while (l != r) {
      int t = (l + r) / 2;
      if (r - l == 1)
        t = r;
      if (sum(t - 1) <= k)
        l = t;
      else
        r = t - 1;
    }
    P p = tree.query(0, l);
    ans += p.first;
    k -= sum(p.second);
    a += sum(p.second);
    add(p.second + 1, -1);
    tree.update(p.second, P(INT_MAX, i));
    P pp = tree.query(p.second);
  }
  cout << ans << endl;
}

Fixed submission:
#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
typedef pair<int, int> P;

#ifndef MAX
#define MAX 800000
#endif

// Range Update Query+Range Minimum Query
template <class T> class RUQ_RMQ {
public:
  int n;
  T dat[MAX], lazy[MAX], DEFAULT;
  bool (*cmp)(T, T);
  void init(
      int n_, bool (*c)(T, T) = [](int a, int b) { return a < b; },
      T d = INT_MAX) {
    cmp = c;
    DEFAULT = d;
    n = 1;
    while (n < n_)
      n <<= 1;
    for (int i = 0; i < 2 * n - 1; i++) {
      dat[i] = lazy[i] = DEFAULT;
    }
  }
  inline void push(int k) {
    if (lazy[k] == DEFAULT)
      return;
    dat[k] = lazy[k];
    if (k < n - 1) {
      lazy[k * 2 + 1] = lazy[k];
      lazy[k * 2 + 2] = lazy[k];
    }
    lazy[k] = DEFAULT;
  }
  inline void update_node(int k) {
    if (cmp(dat[k * 2 + 1], dat[k * 2 + 2]))
      dat[k] = dat[k * 2 + 1];
    else
      dat[k] = dat[k * 2 + 2];
  }
  inline void update(int a, int b, T x, int k, int l, int r) {
    push(k);
    if (r <= a || b <= l)
      return;
    if (a <= l && r <= b) {
      lazy[k] = x;
      push(k);
      return;
    }
    update(a, b, x, k * 2 + 1, l, (l + r) / 2);
    update(a, b, x, k * 2 + 2, (l + r) / 2, r);
    update_node(k);
  }
  inline T query(int a, int b, int k, int l, int r) {
    push(k);
    if (r <= a || b <= l)
      return DEFAULT;
    if (a <= l && r <= b)
      return dat[k];
    T lb = query(a, b, k * 2 + 1, l, (l + r) / 2);
    T rb = query(a, b, k * 2 + 2, (l + r) / 2, r);
    update_node(k);
    if (cmp(lb, rb))
      return lb;
    return rb;
  }
  inline void update(int a, int b, T x) { update(a, b, x, 0, 0, n); }
  inline void update(int a, T x) { update(a, a + 1, x); }
  inline T query(int a, int b) { return query(a, b, 0, 0, n); }
  inline T query(int a) { return query(a, a + 1); }
};

int bit[300000];
void add(int k, int x) {
  k++;
  while (k < 300000) {
    bit[k] += x;
    k += k & -k;
  }
}
int sum(int k) {
  k++;
  int ans = 0;
  while (k) {
    ans += bit[k];
    k -= k & -k;
  }
  return ans;
}
RUQ_RMQ<P> tree;
int main() {
  string s;
  int k;
  cin >> s >> k;
  rep(i, s.size() - 1) add(i + 1, 1);
  tree.init(
      s.size(), [](P a, P b) { return a < b; }, P(INT_MAX, INT_MAX));
  rep(i, s.size()) tree.update(i, P(s[i], i));
  string ans;
  int a = k;
  rep(i, s.size()) {
    int l = 1, r = s.size();
    while (l != r) {
      int t = (l + r) / 2;
      if (r - l == 1)
        t = r;
      if (sum(t - 1) <= k)
        l = t;
      else
        r = t - 1;
    }
    P p = tree.query(0, l);
    ans += p.first;
    k -= sum(p.second);
    a += sum(p.second);
    add(p.second + 1, -1);
    tree.update(p.second, P(INT_MAX, i));
    P pp = tree.query(p.second);
  }
  cout << ans << endl;
}