Problem p03580 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
struct fast_ios {
  fast_ios() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  };
} fast_ios_;
#define FOR(i, begin, end) for (int i = (begin); i < (end); i++)
#define REP(i, n) FOR(i, 0, n)
#define IFOR(i, begin, end) for (int i = (end)-1; i >= (begin); i--)
#define IREP(i, n) IFOR(i, 0, n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(), v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x)                                                      \
  distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x)                                                      \
  distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define Max(a, b) a = max(a, b)
#define Min(a, b) a = min(a, b)
#define bit(n) (1LL << (n))
#define bit_exist(x, n) ((x >> n) & 1)
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v)                                                              \
  cout << #v << "=" << endl;                                                   \
  REP(i_debug, v.size()) { cout << v[i_debug] << ","; }                        \
  cout << endl;
#define mdebug(m)                                                              \
  cout << #m << "=" << endl;                                                   \
  REP(i_debug, m.size()) {                                                     \
    REP(j_debug, m[i_debug].size()) { cout << m[i_debug][j_debug] << ","; }    \
    cout << endl;                                                              \
  }
#define pb push_back
#define f first
#define s second
#define int long long
#define INF 1000000000000000000
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  for (int i = 0; i < v.size(); i++) {
    cout << v[i];
    if (i != v.size() - 1)
      cout << endl;
  };
  return os;
}
template <typename T> void Out(T x) { cout << x << endl; }
template <typename T1, typename T2> void Ans(bool f, T1 y, T2 n) {
  if (f)
    Out(y);
  else
    Out(n);
}

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using PiP = pair<int, Pii>;
using PPi = pair<Pii, int>;
using bools = vector<bool>;
using pairs = vector<Pii>;

// int dx[4] = {1,0,-1,0};
// int dy[4] = {0,1,0,-1};
// char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
// const int mod = 998244353;
// #define Add(x, y) x = (x + (y)) % mod
// #define Mult(x, y) x = (x * (y)) % mod

signed main() {

  int N;
  cin >> N;
  string s;
  cin >> s;

  int ans = 0;
  vec v;
  bool z = false;
  int tmp = 0;
  REP(i, N + 1) {
    if (i == N || (s[i] == '0' && z)) {
      if (tmp)
        v.pb(tmp);
      if (SZ(v) >= 2) {
        // vdebug(v);

        int n = SZ(v);
        REP(j, n) assert(v[j] > 0);
        // 0使わない 1 1残し 2 1消費　3 全消し
        mat dp(n, vec(4, -INF));
        dp[0][0] = 0;
        FOR(j, 1, n) {

          REP(k, 4) Max(dp[j][0], dp[j - 1][k]);
          REP(k, 3) Max(dp[j][3], dp[j - 1][k] + v[j]);

          if (v[j] >= 2) {
            REP(k, 3) Max(dp[j][1], dp[j - 1][k] + v[j] - 1);

            Max(dp[j][2], dp[j - 1][0] + v[j - 1]);
            Max(dp[j][2], dp[j - 1][1] + 1);
            Max(dp[j][2], dp[j - 1][2] + v[j - 1] - 1);
          } else {
            REP(k, 3) Max(dp[j][3], dp[j - 1][k] + v[j] - 1);

            Max(dp[j][3], dp[j - 1][0] + v[j - 1]);
            Max(dp[j][3], dp[j - 1][1] + 1);
            Max(dp[j][3], dp[j - 1][2] + v[j - 1] - 1);
          }

          int m = 0;
          REP(k, 4) Max(m, dp[n - 1][k]);
          // debug(m);
          ans += m;
        }
      }
      v = vec(0);
    } else if (s[i] == '0' && !z) {
      v.pb(tmp);
      tmp = 0;
      z = true;
    } else if (s[i] == '1') {
      tmp++;
      z = false;
    }
  }
  Out(ans);

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
struct fast_ios {
  fast_ios() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  };
} fast_ios_;
#define FOR(i, begin, end) for (int i = (begin); i < (end); i++)
#define REP(i, n) FOR(i, 0, n)
#define IFOR(i, begin, end) for (int i = (end)-1; i >= (begin); i--)
#define IREP(i, n) IFOR(i, 0, n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(), v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x)                                                      \
  distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x)                                                      \
  distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define Max(a, b) a = max(a, b)
#define Min(a, b) a = min(a, b)
#define bit(n) (1LL << (n))
#define bit_exist(x, n) ((x >> n) & 1)
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v)                                                              \
  cout << #v << "=" << endl;                                                   \
  REP(i_debug, v.size()) { cout << v[i_debug] << ","; }                        \
  cout << endl;
#define mdebug(m)                                                              \
  cout << #m << "=" << endl;                                                   \
  REP(i_debug, m.size()) {                                                     \
    REP(j_debug, m[i_debug].size()) { cout << m[i_debug][j_debug] << ","; }    \
    cout << endl;                                                              \
  }
#define pb push_back
#define f first
#define s second
#define int long long
#define INF 1000000000000000000
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  for (int i = 0; i < v.size(); i++) {
    cout << v[i];
    if (i != v.size() - 1)
      cout << endl;
  };
  return os;
}
template <typename T> void Out(T x) { cout << x << endl; }
template <typename T1, typename T2> void Ans(bool f, T1 y, T2 n) {
  if (f)
    Out(y);
  else
    Out(n);
}

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using PiP = pair<int, Pii>;
using PPi = pair<Pii, int>;
using bools = vector<bool>;
using pairs = vector<Pii>;

// int dx[4] = {1,0,-1,0};
// int dy[4] = {0,1,0,-1};
// char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
// const int mod = 998244353;
// #define Add(x, y) x = (x + (y)) % mod
// #define Mult(x, y) x = (x * (y)) % mod

signed main() {

  int N;
  cin >> N;
  string s;
  cin >> s;

  int ans = 0;
  vec v;
  bool z = false;
  int tmp = 0;
  REP(i, N + 1) {
    if (i == N || (s[i] == '0' && z)) {
      if (tmp)
        v.pb(tmp);
      if (SZ(v) >= 2) {
        // vdebug(v);

        int n = SZ(v);
        REP(j, n) assert(v[j] > 0);
        // 0使わない 1 1残し 2 1消費　3 全消し
        mat dp(n, vec(4, -INF));
        dp[0][0] = 0;
        FOR(j, 1, n) {

          REP(k, 4) Max(dp[j][0], dp[j - 1][k]);
          REP(k, 3) Max(dp[j][3], dp[j - 1][k] + v[j]);

          if (v[j] >= 2) {
            REP(k, 3) Max(dp[j][1], dp[j - 1][k] + v[j] - 1);

            Max(dp[j][2], dp[j - 1][0] + v[j - 1]);
            Max(dp[j][2], dp[j - 1][1] + 1);
            Max(dp[j][2], dp[j - 1][2] + v[j - 1] - 1);
          } else {
            REP(k, 3) Max(dp[j][3], dp[j - 1][k] + v[j] - 1);

            Max(dp[j][3], dp[j - 1][0] + v[j - 1]);
            Max(dp[j][3], dp[j - 1][1] + 1);
            Max(dp[j][3], dp[j - 1][2] + v[j - 1] - 1);
          }

          int m = 0;
          REP(k, 4) Max(m, dp[n - 1][k]);
          // debug(m);
          ans += m;
        }
      }
      v = vec(0);
    } else if (s[i] == '0' && !z) {
      if (tmp)
        v.pb(tmp);
      tmp = 0;
      z = true;
    } else if (s[i] == '1') {
      tmp++;
      z = false;
    }
  }
  Out(ans);

  return 0;
}