Problem p03611 (C++)

Buggy submission (status: Runtime Error):

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#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;

// conversion
//------------------------------------------
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();
}

// math
//-------------------------------------------
template <class T> inline T sqr(T x) { return x * x; }

// typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

// container util
//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#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 SORT(c) sort((c).begin(), (c).end())

// repetition
//------------------------------------------
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)

// constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);

// clear memory
#define CLR(a) memset((a), 0, sizeof(a))

// debug
#define dump(x) cerr << #x << '=' << (x) << endl;
#define debug(x)                                                               \
  cerr << #x << '=' << (x) << '(' << 'L' << __LINE__ << ')' << ' ' << __FILE__ \
       << endl;

const int MAX_N = 123456;
// vector<int> A;
int A[MAX_N];
int n;
int main() {
  CLR(A);
  cin >> n;
  // 数が多すぎてPushbackできていない？？　というかいちいち格納しなくても解ける？？？？
  REP(i, n) {
    int a;
    cin >> a;
    A[a]++;
  }
  if (n == 1) {
    cout << 1 << endl;
    return 1;
  }
  int max_ = -1;
  int num = 0;
  REP(i, n) {
    num = 0;
    int a = i;
    if (i - 1 < 0) {
      num = A[i] + A[i + 1];
    } else {
      num = A[i - 1] + A[i] + A[i + 1];
    }
    max_ = max(max_, num);
  }

  cout << max_ << endl;
}


Fixed submission:

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#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;

// conversion
//------------------------------------------
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();
}

// math
//-------------------------------------------
template <class T> inline T sqr(T x) { return x * x; }

// typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

// container util
//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#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 SORT(c) sort((c).begin(), (c).end())

// repetition
//------------------------------------------
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)

// constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);

// clear memory
#define CLR(a) memset((a), 0, sizeof(a))

// debug
#define dump(x) cerr << #x << '=' << (x) << endl;
#define debug(x)                                                               \
  cerr << #x << '=' << (x) << '(' << 'L' << __LINE__ << ')' << ' ' << __FILE__ \
       << endl;

const int MAX_N = 123456;
// vector<int> A;
int A[MAX_N];
int n;
int main() {
  CLR(A);
  cin >> n;
  // 数が多すぎてPushbackできていない？？　というかいちいち格納しなくても解ける？？？？
  REP(i, n) {
    int a;
    cin >> a;
    A[a]++;
  }
  if (n == 1) {
    cout << 1 << endl;
    return 0;
  }
  int max_ = -1;
  int num = 0;
  REP(i, n) {
    num = 0;
    int a = i;
    if (i - 1 < 0) {
      num = A[i] + A[i + 1];
    } else {
      num = A[i - 1] + A[i] + A[i + 1];
    }
    max_ = max(max_, num);
  }

  cout << max_ << endl;
}