Problem p02551 (C++) — buggy submission, verdict: Runtime Error

/*** Template Begin ***/

#pragma region template

// #define USING_BOOST
#define USING_NAMESPACE

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

typedef int64_t i64;
typedef uint64_t u64;

auto init_ = [] {
  std::ios_base::sync_with_stdio(false);
  std::cout << std::fixed;
  return 0;
}();

template <typename T> inline void in(T &x) { std::cin >> x; }

template <typename T, typename... Ts> inline void in(T &t, Ts &...ts) {
  std::cin >> t;
  in(ts...);
}

template <typename T, typename U = std::vector<T>> inline U vin(int n) {
  U v(n);
  for (int i = 0; i < n; ++i) {
    std::cin >> v[i];
  }
  return v;
}

template <typename T, typename U = std::vector<T>, typename V = std::vector<U>>
inline V vin(int h, int w) {
  V vv(h, U(w));
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      std::cin >> vv[i][j];
    }
  }
  return vv;
}

template <typename T> inline void out(const T &x) {
  std::cout << x << std::endl;
}

template <char delimiter = ' ', typename T, typename... Ts>
inline void out(const T &t, const Ts &...ts) {
  std::cout << t << delimiter;
  out(ts...);
}

template <char delimiter = ' ', typename T>
inline void vout(const T &v, int n) {
  for (int i = 0; i < n; ++i) {
    if (i)
      std::cout << delimiter;
    std::cout << v[i];
  }
  std::cout << std::endl;
}

template <char delimiter = ' ', typename T>
inline void vout(const T &v, int h, int w) {
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      if (j)
        std::cout << delimiter;
      std::cout << v[i][j];
    }
    std::cout << std::endl;
  }
}

template <typename T, size_t D> struct multi_vector_type {
  using type = std::vector<typename multi_vector_type<T, D - 1>::type>;
};

template <typename T> struct multi_vector_type<T, 1> {
  using type = std::vector<T>;
};

template <typename T> struct multi_vector_type<T, 0> {
  using type = T;
};

template <typename T, size_t D>
using multi_vector = typename multi_vector_type<T, D>::type;

template <typename T, size_t D, class = typename std::enable_if<D == 0>::type>
T make_vector(const T &val = T()) {
  return val;
}

template <typename T, size_t D = 1, typename... Ts,
          class = typename std::enable_if<D != 0>::type>
multi_vector<T, D> make_vector(size_t n, Ts &&...args) {
  return multi_vector<T, D>(n, make_vector<T, D - 1>(args...));
}

namespace detail {

template <typename F> struct Debug {
  const char *delim_ = "\\n";
  F fun;

  Debug(F f) : fun(f) {}

  ~Debug() { fun(delim_); }

  Debug &delim(const char *d) {
    delim_ = d;
    return *this;
  }
};

std::deque<std::string> split(const std::string &s, char c) {
  std::deque<std::string> v;
  std::stringstream ss(s);
  std::string x;
  while (std::getline(ss, x, c))
    v.emplace_back(x);
  return v;
}

template <typename T>
void deb(const char *delim, std::deque<std::string> v, T a) {
  std::cerr << v[0].substr(v[0][0] == ' ', v[0].length()) << " = " << a << '\\n';
  std::cerr << std::flush;
}

template <typename T, typename... Args>
void deb(const char *delim, std::deque<std::string> v, T a, Args... args) {
  std::cerr << v[0].substr(v[0][0] == ' ', v[0].length()) << " = " << a
            << delim;
  v.pop_front();
  deb(delim, std::move(v), args...);
}

template <typename... Args> auto wrap(std::deque<std::string> v, Args... args) {
  auto f = [=](const char *delim = "\\n") { deb(delim, v, args...); };

  return Debug<decltype(f)>(f);
}
} // namespace detail

#define debug(args...) ::detail::wrap(::detail::split(#args, ','), args)

#ifdef USING_BOOST

#include <boost/math/common_factor.hpp>
#include <boost/range.hpp>
#include <boost/range/adaptors.hpp>
#include <boost/range/algorithm.hpp>
#include <boost/range/algorithm_ext.hpp>
#include <boost/range/irange.hpp>
#include <boost/range/numeric.hpp>

inline auto rep(int begin, int end) {
  if (begin > end) {
    return boost::irange(0, 0);
  } else {
    return boost::irange(begin, end);
  }
}

inline auto rep(int begin, int end, int step) {
  if ((step > 0 && begin > end) || (step < 0 && begin < end)) {
    return boost::irange(0, 0, step);
  } else {
    return boost::irange(begin, end, step);
  }
}

#endif

#ifdef USING_NAMESPACE
using namespace std;

#ifdef USING_BOOST
using namespace boost;
using namespace boost::adaptors;
#endif
#endif

#pragma endregion

/*** Template End ***/

struct B {
  i64 width, length;
};

int main() {
  i64 n, q;
  in(n, q);

  pair<i64, i64> LU(n - 2, n - 2);
  map<i64, B> L, U;

  i64 ans = (n - 2) * (n - 2);

  for (int i = 0; i < q; i++) {
    int d, x;
    in(d, x);
    x -= 2;

    if (d == 1) {
      if (LU.second > x) {
        ans -= LU.first;

        if (LU.second != x + 1) {
          B tmp = {LU.second - x - 1, LU.first};
          U[x + 1] = tmp;
        }

        LU.second = x;
      } else {
        auto [pos, target] = *prev(U.upper_bound(x));
        U.erase(pos);

        ans -= target.length;

        B part1 = {x - pos, target.length};
        B part2 = {target.width - (x - pos - 1), target.length};

        if (part1.width > 0) {
          U[pos] = part1;
        }

        if (part2.width > 0) {
          U[x + 1] = part2;
        }
      }
    } else {
      if (LU.first > x) {
        ans -= LU.second;

        if (LU.first != x + 1) {
          B tmp = {LU.first - x - 1, LU.second};
          L[x + 1] = tmp;
        }

        LU.first = x;
      } else {
        auto [pos, target] = *prev(L.upper_bound(x));
        L.erase(pos);

        ans -= target.length;

        B part1 = {x - pos, target.length};
        B part2 = {target.width - (x - pos - 1), target.length};

        if (part1.width > 0) {
          L[pos] = part1;
        }

        if (part2.width > 0) {
          L[x + 1] = part2;
        }
      }
    }
  }

  out(ans);
}


Error: 0

Fixed submission:

/*** Template Begin ***/

#pragma region template

// #define USING_BOOST
#define USING_NAMESPACE

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

typedef int64_t i64;
typedef uint64_t u64;

auto init_ = [] {
  std::ios_base::sync_with_stdio(false);
  std::cout << std::fixed;
  return 0;
}();

template <typename T> inline void in(T &x) { std::cin >> x; }

template <typename T, typename... Ts> inline void in(T &t, Ts &...ts) {
  std::cin >> t;
  in(ts...);
}

template <typename T, typename U = std::vector<T>> inline U vin(int n) {
  U v(n);
  for (int i = 0; i < n; ++i) {
    std::cin >> v[i];
  }
  return v;
}

template <typename T, typename U = std::vector<T>, typename V = std::vector<U>>
inline V vin(int h, int w) {
  V vv(h, U(w));
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      std::cin >> vv[i][j];
    }
  }
  return vv;
}

template <typename T> inline void out(const T &x) {
  std::cout << x << std::endl;
}

template <char delimiter = ' ', typename T, typename... Ts>
inline void out(const T &t, const Ts &...ts) {
  std::cout << t << delimiter;
  out(ts...);
}

template <char delimiter = ' ', typename T>
inline void vout(const T &v, int n) {
  for (int i = 0; i < n; ++i) {
    if (i)
      std::cout << delimiter;
    std::cout << v[i];
  }
  std::cout << std::endl;
}

template <char delimiter = ' ', typename T>
inline void vout(const T &v, int h, int w) {
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      if (j)
        std::cout << delimiter;
      std::cout << v[i][j];
    }
    std::cout << std::endl;
  }
}

template <typename T, size_t D> struct multi_vector_type {
  using type = std::vector<typename multi_vector_type<T, D - 1>::type>;
};

template <typename T> struct multi_vector_type<T, 1> {
  using type = std::vector<T>;
};

template <typename T> struct multi_vector_type<T, 0> {
  using type = T;
};

template <typename T, size_t D>
using multi_vector = typename multi_vector_type<T, D>::type;

template <typename T, size_t D, class = typename std::enable_if<D == 0>::type>
T make_vector(const T &val = T()) {
  return val;
}

template <typename T, size_t D = 1, typename... Ts,
          class = typename std::enable_if<D != 0>::type>
multi_vector<T, D> make_vector(size_t n, Ts &&...args) {
  return multi_vector<T, D>(n, make_vector<T, D - 1>(args...));
}

namespace detail {

template <typename F> struct Debug {
  const char *delim_ = "\\n";
  F fun;

  Debug(F f) : fun(f) {}

  ~Debug() { fun(delim_); }

  Debug &delim(const char *d) {
    delim_ = d;
    return *this;
  }
};

std::deque<std::string> split(const std::string &s, char c) {
  std::deque<std::string> v;
  std::stringstream ss(s);
  std::string x;
  while (std::getline(ss, x, c))
    v.emplace_back(x);
  return v;
}

template <typename T>
void deb(const char *delim, std::deque<std::string> v, T a) {
  std::cerr << v[0].substr(v[0][0] == ' ', v[0].length()) << " = " << a << '\\n';
  std::cerr << std::flush;
}

template <typename T, typename... Args>
void deb(const char *delim, std::deque<std::string> v, T a, Args... args) {
  std::cerr << v[0].substr(v[0][0] == ' ', v[0].length()) << " = " << a
            << delim;
  v.pop_front();
  deb(delim, std::move(v), args...);
}

template <typename... Args> auto wrap(std::deque<std::string> v, Args... args) {
  auto f = [=](const char *delim = "\\n") { deb(delim, v, args...); };

  return Debug<decltype(f)>(f);
}
} // namespace detail

#define debug(args...) ::detail::wrap(::detail::split(#args, ','), args)

#ifdef USING_BOOST

#include <boost/math/common_factor.hpp>
#include <boost/range.hpp>
#include <boost/range/adaptors.hpp>
#include <boost/range/algorithm.hpp>
#include <boost/range/algorithm_ext.hpp>
#include <boost/range/irange.hpp>
#include <boost/range/numeric.hpp>

inline auto rep(int begin, int end) {
  if (begin > end) {
    return boost::irange(0, 0);
  } else {
    return boost::irange(begin, end);
  }
}

inline auto rep(int begin, int end, int step) {
  if ((step > 0 && begin > end) || (step < 0 && begin < end)) {
    return boost::irange(0, 0, step);
  } else {
    return boost::irange(begin, end, step);
  }
}

#endif

#ifdef USING_NAMESPACE
using namespace std;

#ifdef USING_BOOST
using namespace boost;
using namespace boost::adaptors;
#endif
#endif

#pragma endregion

/*** Template End ***/

struct B {
  i64 width, length;
};

int main() {
  i64 n, q;
  in(n, q);

  pair<i64, i64> LU(n - 2, n - 2);
  map<i64, B> L, U;

  i64 ans = (n - 2) * (n - 2);

  for (int i = 0; i < q; i++) {
    int d, x;
    in(d, x);
    x -= 2;

    if (d == 1) {
      if (LU.second > x) {
        ans -= LU.first;

        if (LU.second != x + 1) {
          B tmp = {LU.second - x - 1, LU.first};
          U[x + 1] = tmp;
        }

        LU.second = x;
      } else {
        auto [pos, target] = *prev(U.upper_bound(x));
        U.erase(pos);

        ans -= target.length;

        B part1 = {x - pos - 1, target.length};
        B part2 = {target.width - (x - pos), target.length};

        if (part1.width > 0) {
          U[pos] = part1;
        }

        if (part2.width > 0) {
          U[x + 1] = part2;
        }
      }
    } else {
      if (LU.first > x) {
        ans -= LU.second;

        if (LU.first != x + 1) {
          B tmp = {LU.first - x - 1, LU.second};
          L[x + 1] = tmp;
        }

        LU.first = x;
      } else {
        auto [pos, target] = *prev(L.upper_bound(x));
        L.erase(pos);

        ans -= target.length;

        B part1 = {x - pos - 1, target.length};
        B part2 = {target.width - (x - pos), target.length};

        if (part1.width > 0) {
          L[pos] = part1;
        }

        if (part2.width > 0) {
          L[x + 1] = part2;
        }
      }
    }
  }

  out(ans);
}