Problem p03848 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <cmath>
#include <fstream>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <vector>

using namespace std;

#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

long long gcd(long long a, long long b) {
  if (a < b) {
    swap(a, b);
  }
  while (b) {
    long long r = a % b;
    a = b;
    b = r;
  }
  return a;
}

long long lcm(long long a, long long b) { return (a * b) / gcd(a, b); }

int isPrim(int a) {
  if (a == 1) {
    return 0;
  }
  for (int i = 2; i <= (a + 1) / 2; i++) {
    if (a % i == 0) {
      return 0;
    }
  }
  return 1;
}

long long mod_pow(long long x, long long n, long long mod) {
  // xのn乗を計算するのにn乗を2進表記にして計算
  // x^22 = x^16 + x^4 + x^2
  long long ret = 1;
  while (n > 0) {
    if (n % 2 == 1) {
      ret = (ret * x) % mod; // 答えに付加
    }
    x = (x * x) % mod; // 2乗
    n = n / 2;
  }
  return ret;
}

struct XX {
  int u;
  int v;
  int t;
};

class xxIntu {
public:
  bool operator()(const XX &riLeft, const XX &riRight) const {
    // 第2条件
    if ((riLeft.t) == (riRight.t)) {
      return riLeft.u <
             riRight.u; //<:昇順(小さいものから順番)、>:降順(大きいものから順番)
    }
    // 第1条件
    return (riLeft.t) < (riRight.t);
  }
};
/*bool operator< (const XX &riLeft, const XX &riRight){
    return riLeft.d < riRight.d;
};*/

int index(string in) {
  if (in == "A") {
    return 0;
  } else if (in == "B") {
    return 1;
  } else if (in == "C") {
    return 2;
  } else if (in == "D") {
    return 3;
  } else if (in == "E") {
    return 4;
  } else if (in == "F") {
    return 5;
  } else if (in == "G") {
    return 6;
  } else if (in == "H") {
    return 7;
  } else if (in == "I") {
    return 8;
  } else if (in == "J") {
    return 9;
  } else if (in == "K") {
    return 10;
  } else if (in == "L") {
    return 11;
  } else if (in == "M") {
    return 12;
  } else if (in == "N") {
    return 13;
  } else if (in == "O") {
    return 14;
  } else if (in == "P") {
    return 15;
  } else if (in == "Q") {
    return 16;
  } else if (in == "R") {
    return 17;
  } else if (in == "S") {
    return 18;
  } else if (in == "T") {
    return 19;
  } else if (in == "U") {
    return 20;
  } else if (in == "V") {
    return 21;
  } else if (in == "W") {
    return 22;
  } else if (in == "X") {
    return 23;
  } else if (in == "Y") {
    return 24;
  } else if (in == "Z") {
    return 25;
  }
  return -1;
}

string rindex(int in) {
  if (in == 65) {
    return "A";
  } else if (in == 66) {
    return "B";
  } else if (in == 67) {
    return "C";
  } else if (in == 68) {
    return "D";
  } else if (in == 69) {
    return "E";
  } else if (in == 70) {
    return "F";
  } else if (in == 71) {
    return "G";
  } else if (in == 72) {
    return "H";
  } else if (in == 73) {
    return "I";
  } else if (in == 74) {
    return "J";
  } else if (in == 75) {
    return "K";
  } else if (in == 76) {
    return "L";
  } else if (in == 77) {
    return "M";
  } else if (in == 78) {
    return "N";
  } else if (in == 79) {
    return "O";
  } else if (in == 80) {
    return "P";
  } else if (in == 81) {
    return "Q";
  } else if (in == 82) {
    return "R";
  } else if (in == 83) {
    return "S";
  } else if (in == 84) {
    return "T";
  } else if (in == 85) {
    return "U";
  } else if (in == 86) {
    return "V";
  } else if (in == 87) {
    return "W";
  } else if (in == 88) {
    return "X";
  } else if (in == 89) {
    return "Y";
  } else if (in == 90) {
    return "Z";
  }
  return "";
}

int ppar[200001];
int rrank[200001];

void init(int n) {
  for (int i = 1; i <= n; i++) {
    ppar[i] = i;
    rrank[i] = 0;
  }
}

int find(int x) {
  if (ppar[x] == x) {
    return x;
  } else {
    return ppar[x] = find(ppar[x]);
  }
}

void unite(int x, int y) {
  x = find(x);
  y = find(y);
  if (x == y) {
    return;
  }
  if (rrank[x] < rrank[y]) {
    ppar[x] = ppar[y];
  } else {
    ppar[y] = x;
    if (rrank[x] == rrank[y]) {
      rrank[x]++;
    }
  }
}
bool same(int x, int y) { return find(x) == find(y); }

int main(int argc, const char *argv[]) {
  // std::ios::sync_with_stdio(false);
  // scanf("%s",S);
  // scanf("%d",&N);
  // getline(cin, target);
  // cin >> x >> y;
  // テスト用
  // ifstream ifs( "1_06.txt" );
  // ifs >> a;
  // ここから

  int N;
  cin >> N;
  int A[10000];
  for (int i = 0; i < N; i++) {
    cin >> A[i];
  }
  sort(A, A + N);

  for (int i = 0; i < N; i++) {

    if (N % 2 == 0) {
      // cout << (((i+1)/2)+(i+1)%2)*2-1;

      if (A[i] != (((i + 1) / 2) + (i + 1) % 2) * 2 - 1) {
        cout << 0 << endl;
        return 0;
      }
    } else {
      // cout << ((i/2)+i%2)*2;

      if (i == 0 && A[i] != 0) {
        cout << 0 << endl;
        return 0;
      } else if (A[i] != ((i / 2) + i % 2) * 2) {
        cout << 0 << endl;
        return 0;
      }
    }
  }

  int ans = 1;
  int M = N / 2;
  for (int i = 0; i < M; i++) {
    ans = 2 * ans;
    ans = ans % 1000000007;
  }

  cout << ans << endl;

  // ここまで
  // cout << "ans" << endl;改行含む
  // printf("%.0f\n",ans);//小数点以下表示なし
  // printf("%.7f\n",p);
  // printf("%f\n",pow(2,ans.size()));

  return 0;
}

Fixed submission:
#include <algorithm>
#include <cmath>
#include <fstream>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <vector>

using namespace std;

#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

long long gcd(long long a, long long b) {
  if (a < b) {
    swap(a, b);
  }
  while (b) {
    long long r = a % b;
    a = b;
    b = r;
  }
  return a;
}

long long lcm(long long a, long long b) { return (a * b) / gcd(a, b); }

int isPrim(int a) {
  if (a == 1) {
    return 0;
  }
  for (int i = 2; i <= (a + 1) / 2; i++) {
    if (a % i == 0) {
      return 0;
    }
  }
  return 1;
}

long long mod_pow(long long x, long long n, long long mod) {
  // xのn乗を計算するのにn乗を2進表記にして計算
  // x^22 = x^16 + x^4 + x^2
  long long ret = 1;
  while (n > 0) {
    if (n % 2 == 1) {
      ret = (ret * x) % mod; // 答えに付加
    }
    x = (x * x) % mod; // 2乗
    n = n / 2;
  }
  return ret;
}

struct XX {
  int u;
  int v;
  int t;
};

class xxIntu {
public:
  bool operator()(const XX &riLeft, const XX &riRight) const {
    // 第2条件
    if ((riLeft.t) == (riRight.t)) {
      return riLeft.u <
             riRight.u; //<:昇順(小さいものから順番)、>:降順(大きいものから順番)
    }
    // 第1条件
    return (riLeft.t) < (riRight.t);
  }
};
/*bool operator< (const XX &riLeft, const XX &riRight){
    return riLeft.d < riRight.d;
};*/

int index(string in) {
  if (in == "A") {
    return 0;
  } else if (in == "B") {
    return 1;
  } else if (in == "C") {
    return 2;
  } else if (in == "D") {
    return 3;
  } else if (in == "E") {
    return 4;
  } else if (in == "F") {
    return 5;
  } else if (in == "G") {
    return 6;
  } else if (in == "H") {
    return 7;
  } else if (in == "I") {
    return 8;
  } else if (in == "J") {
    return 9;
  } else if (in == "K") {
    return 10;
  } else if (in == "L") {
    return 11;
  } else if (in == "M") {
    return 12;
  } else if (in == "N") {
    return 13;
  } else if (in == "O") {
    return 14;
  } else if (in == "P") {
    return 15;
  } else if (in == "Q") {
    return 16;
  } else if (in == "R") {
    return 17;
  } else if (in == "S") {
    return 18;
  } else if (in == "T") {
    return 19;
  } else if (in == "U") {
    return 20;
  } else if (in == "V") {
    return 21;
  } else if (in == "W") {
    return 22;
  } else if (in == "X") {
    return 23;
  } else if (in == "Y") {
    return 24;
  } else if (in == "Z") {
    return 25;
  }
  return -1;
}

string rindex(int in) {
  if (in == 65) {
    return "A";
  } else if (in == 66) {
    return "B";
  } else if (in == 67) {
    return "C";
  } else if (in == 68) {
    return "D";
  } else if (in == 69) {
    return "E";
  } else if (in == 70) {
    return "F";
  } else if (in == 71) {
    return "G";
  } else if (in == 72) {
    return "H";
  } else if (in == 73) {
    return "I";
  } else if (in == 74) {
    return "J";
  } else if (in == 75) {
    return "K";
  } else if (in == 76) {
    return "L";
  } else if (in == 77) {
    return "M";
  } else if (in == 78) {
    return "N";
  } else if (in == 79) {
    return "O";
  } else if (in == 80) {
    return "P";
  } else if (in == 81) {
    return "Q";
  } else if (in == 82) {
    return "R";
  } else if (in == 83) {
    return "S";
  } else if (in == 84) {
    return "T";
  } else if (in == 85) {
    return "U";
  } else if (in == 86) {
    return "V";
  } else if (in == 87) {
    return "W";
  } else if (in == 88) {
    return "X";
  } else if (in == 89) {
    return "Y";
  } else if (in == 90) {
    return "Z";
  }
  return "";
}

int ppar[200001];
int rrank[200001];

void init(int n) {
  for (int i = 1; i <= n; i++) {
    ppar[i] = i;
    rrank[i] = 0;
  }
}

int find(int x) {
  if (ppar[x] == x) {
    return x;
  } else {
    return ppar[x] = find(ppar[x]);
  }
}

void unite(int x, int y) {
  x = find(x);
  y = find(y);
  if (x == y) {
    return;
  }
  if (rrank[x] < rrank[y]) {
    ppar[x] = ppar[y];
  } else {
    ppar[y] = x;
    if (rrank[x] == rrank[y]) {
      rrank[x]++;
    }
  }
}
bool same(int x, int y) { return find(x) == find(y); }

int main(int argc, const char *argv[]) {
  // std::ios::sync_with_stdio(false);
  // scanf("%s",S);
  // scanf("%d",&N);
  // getline(cin, target);
  // cin >> x >> y;
  // テスト用
  // ifstream ifs( "1_06.txt" );
  // ifs >> a;
  // ここから

  int N;
  cin >> N;
  int A[100000];
  for (int i = 0; i < N; i++) {
    cin >> A[i];
  }
  sort(A, A + N);

  for (int i = 0; i < N; i++) {

    if (N % 2 == 0) {
      // cout << (((i+1)/2)+(i+1)%2)*2-1;

      if (A[i] != (((i + 1) / 2) + (i + 1) % 2) * 2 - 1) {
        cout << 0 << endl;
        return 0;
      }
    } else {
      // cout << ((i/2)+i%2)*2;

      if (i == 0 && A[i] != 0) {
        cout << 0 << endl;
        return 0;
      } else if (A[i] != ((i / 2) + i % 2) * 2) {
        cout << 0 << endl;
        return 0;
      }
    }
  }

  int ans = 1;
  int M = N / 2;
  for (int i = 0; i < M; i++) {
    ans = 2 * ans;
    ans = ans % 1000000007;
  }

  cout << ans << endl;

  // ここまで
  // cout << "ans" << endl;改行含む
  // printf("%.0f\n",ans);//小数点以下表示なし
  // printf("%.7f\n",p);
  // printf("%f\n",pow(2,ans.size()));

  return 0;
}