Problem p03954 (C++)

Buggy submission (status: Runtime Error):
// Copyright (C) 2017 __debug.

// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; version 3

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program; If not, see <http://www.gnu.org/licenses/>.

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/priority_queue.hpp>

#define x first
#define y second
#define MP std::make_pair
#define SZ(x) ((int)(x).size())
#define ALL(x) (x).begin(), (x).end()
#define DEBUG(...) fprintf(stderr, __VA_ARGS__)
#ifdef __linux__
#define getchar getchar_unlocked
#define putchar putchar_unlocked
#endif

using std::pair;
using std::string;
using std::vector;

typedef long long LL;
typedef pair<int, int> Pii;

const int oo = 0x3f3f3f3f;

template <typename T> inline bool chkmax(T &a, T b) {
  return a < b ? a = b, true : false;
}
template <typename T> inline bool chkmin(T &a, T b) {
  return b < a ? a = b, true : false;
}
string procStatus() {
  std::ifstream t("/proc/self/status");
  return string(std::istreambuf_iterator<char>(t),
                std::istreambuf_iterator<char>());
}
template <typename T> T read(T &x) {
  int f = 1;
  char ch = getchar();
  for (; !isdigit(ch); ch = getchar())
    f = (ch == '-' ? -1 : 1);
  for (x = 0; isdigit(ch); ch = getchar())
    x = 10 * x + ch - '0';
  return x *= f;
}
template <typename T> void write(T x) {
  if (x == 0) {
    putchar('0');
    return;
  }
  if (x < 0) {
    putchar('-');
    x = -x;
  }
  static char s[20];
  int top = 0;
  for (; x; x /= 10)
    s[++top] = x % 10 + '0';
  while (top)
    putchar(s[top--]);
}
// EOT

const int MAXN = 1e5 + 5;

int N;
int A[MAXN];

void input() {
  read(N);
  for (int i = 1; i < N * 2; ++i) {
    read(A[i]);
  }
}

int get(int x) {
  static int B[MAXN];

  for (int i = 1; i < N * 2; ++i) {
    B[i] = (A[i] >= x);
  }
  for (int i = 1; i < N; ++i) {
    if (B[N - i + 1] == B[N - i])
      return B[N - i];
    if (B[N + i - 1] == B[N + i])
      return B[N + i];
  }
  return B[N] ^ (~N & 1);
}

void solve() {
  int l = 1, r = N * 2;
  while (l + 1 < r) {
    int mid = (l + r) >> 1;
    int t = get(mid);
    if (t == 0)
      r = mid;
    else
      l = mid;
  }

  printf("%d\n", l);
}

int main() {
#ifdef __DEBUG
  freopen("D.in", "r", stdin);
  freopen("D.out", "w", stdout);
#endif

  input();
  solve();

  return 0;
}

// 当时轻别意中人，山长水远知何处。
//     -- 晏殊《踏莎行·碧海无波》


Fixed submission:
// Copyright (C) 2017 __debug.

// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; version 3

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program; If not, see <http://www.gnu.org/licenses/>.

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/priority_queue.hpp>

#define x first
#define y second
#define MP std::make_pair
#define SZ(x) ((int)(x).size())
#define ALL(x) (x).begin(), (x).end()
#define DEBUG(...) fprintf(stderr, __VA_ARGS__)
#ifdef __linux__
#define getchar getchar_unlocked
#define putchar putchar_unlocked
#endif

using std::pair;
using std::string;
using std::vector;

typedef long long LL;
typedef pair<int, int> Pii;

const int oo = 0x3f3f3f3f;

template <typename T> inline bool chkmax(T &a, T b) {
  return a < b ? a = b, true : false;
}
template <typename T> inline bool chkmin(T &a, T b) {
  return b < a ? a = b, true : false;
}
string procStatus() {
  std::ifstream t("/proc/self/status");
  return string(std::istreambuf_iterator<char>(t),
                std::istreambuf_iterator<char>());
}
template <typename T> T read(T &x) {
  int f = 1;
  char ch = getchar();
  for (; !isdigit(ch); ch = getchar())
    f = (ch == '-' ? -1 : 1);
  for (x = 0; isdigit(ch); ch = getchar())
    x = 10 * x + ch - '0';
  return x *= f;
}
template <typename T> void write(T x) {
  if (x == 0) {
    putchar('0');
    return;
  }
  if (x < 0) {
    putchar('-');
    x = -x;
  }
  static char s[20];
  int top = 0;
  for (; x; x /= 10)
    s[++top] = x % 10 + '0';
  while (top)
    putchar(s[top--]);
}
// EOT

const int MAXN = 2e5 + 5;

int N;
int A[MAXN];

void input() {
  read(N);
  for (int i = 1; i < N * 2; ++i) {
    read(A[i]);
  }
}

int get(int x) {
  static int B[MAXN];

  for (int i = 1; i < N * 2; ++i) {
    B[i] = (A[i] >= x);
  }
  for (int i = 1; i < N; ++i) {
    if (B[N - i + 1] == B[N - i])
      return B[N - i];
    if (B[N + i - 1] == B[N + i])
      return B[N + i];
  }
  return B[N] ^ (~N & 1);
}

void solve() {
  int l = 1, r = N * 2;
  while (l + 1 < r) {
    int mid = (l + r) >> 1;
    int t = get(mid);
    if (t == 0)
      r = mid;
    else
      l = mid;
  }

  printf("%d\n", l);
}

int main() {
#ifdef __DEBUG
  freopen("D.in", "r", stdin);
  freopen("D.out", "w", stdout);
#endif

  input();
  solve();

  return 0;
}

// 当时轻别意中人，山长水远知何处。
//     -- 晏殊《踏莎行·碧海无波》