Problem p00440 (C++) — buggy submission, verdict: Runtime Error

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#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 <utility>
#include <vector>

using namespace std;

inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}
template <class T> inline T sqr(T x) { return x * x; }

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef long long ll;

#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define pb push_back
#define mp make_pair
#define each(i, c)                                                             \\
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define exist(s, e) ((s).find(e) != (s).end())
#define range(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) range(i, 0, n)
#define clr(a, b) memset((a), (b), sizeof(a))
#define dump(x) cerr << #x << " = " << (x) << endl;
#define debug(x)                                                               \\
  cerr << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \\
       << " " << __FILE__ << endl;

const double eps = 1e-10;
const double pi = acos(-1.0);
const ll INF = 1LL << 62;
const int inf = 1 << 29;

int main(void) {
  int n, k;
  while (cin >> n >> k, n | k) {
    // dump(n) dump(k)
    bool seq[100010];
    bool empty = false;
    rep(i, 100010) seq[i] = false;
    rep(i, k) {
      int in;
      cin >> in;
      if (in)
        seq[in - 1] = true;
      else
        empty = true;
    }
    int cmax = 0;
    int l = 0, r = 0;
    rep(i, n) {
      if (seq[i])
        r++;
      else {
        cmax = max(cmax, r - l);
        l = i + 1, r = i + 1;
      }
      // dump(cmax)
    }
    cmax = max(cmax, r - l);
    l = 0, r = 0;
    int mid = -1;
    if (empty) {
      rep(i, n) {
        if (seq[i])
          r++;
        else if (!seq[i] && mid == -1) {
          mid = i;
        } else {
          cmax = max(cmax, r - l);
          l = mid + 1, mid = i, r = i + 1;
        }
        /*dump(i) dump(l) dump(mid) dump(r)
        cout << endl;*/
      }
    }
    cmax = max(cmax, r - l);
    cout << cmax << endl;
  }
  return 0;
}

Error: WA

Fixed submission:

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#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 <utility>
#include <vector>

using namespace std;

inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}
template <class T> inline T sqr(T x) { return x * x; }

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef long long ll;

#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define pb push_back
#define mp make_pair
#define each(i, c)                                                             \\
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define exist(s, e) ((s).find(e) != (s).end())
#define range(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) range(i, 0, n)
#define clr(a, b) memset((a), (b), sizeof(a))
#define dump(x) cerr << #x << " = " << (x) << endl;
#define debug(x)                                                               \\
  cerr << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \\
       << " " << __FILE__ << endl;

const double eps = 1e-10;
const double pi = acos(-1.0);
const ll INF = 1LL << 62;
const int inf = 1 << 29;

int main(void) {
  int n, k;
  while (cin >> n >> k, n | k) {
    dump(n) dump(k) bool seq[100010];
    bool empty = false;
    rep(i, 100010) seq[i] = false;
    rep(i, k) {
      int in;
      cin >> in;
      if (in)
        seq[in - 1] = true;
      else
        empty = true;
    }
    int cmax = 0;
    int l = 0, r = 0;
    rep(i, n) {
      if (seq[i])
        r++;
      else {
        cmax = max(cmax, r - l);
        l = i, r = i + 1;
      }
      // dump(cmax)
    }
    cmax = max(cmax, r - l);
    l = 0, r = 0;
    int mid = -1;
    if (empty) {
      rep(i, n) {
        if (seq[i])
          r++;
        else if (!seq[i] && mid == -1) {
          mid = i;
        } else {
          cmax = max(cmax, r - l);
          l = mid + 1, mid = i, r = i + 1;
        }
        /*dump(i) dump(l) dump(mid) dump(r)
        cout << endl;*/
      }
    }
    cmax = max(cmax, r - l);
    cout << cmax << endl;
  }
  return 0;
}