Problem p00253 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <complex>
#include <cstdio>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

// common
typedef long long i64, ll;

#define BR "\\n"
#define ALL(c) (c).begin(), (c).end()
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define FOR(i, l, r) for (int i = (l); i < (int)(r); ++i)
#define EACH(it, o) for (auto it = (o).begin(); it != (o).end(); ++it)
#define IN(l, v, r) ((l) <= (v) && (v) < (r))

// debug
#ifdef NDEBUG
#define DUMP(x)
#define DUMPLN(x)
#define DEBUG(x)
#define DEBUGLN(x)
#define LINE()
#define LINELN()
#define CHECK(exp, act)
#define STOP(e)
#else
#define DUMP(x) cerr << #x << " = " << (x)
#define DUMPLN(x) DUMP(x) << endl
#define DEBUG(x) DUMP(x) << LINE() << " " << __FILE__
#define DEBUGLN(x) DEBUG(x) << endl
#define LINE() cerr << " (L" << __LINE__ << ")"
#define LINELN() LINE() << endl
#define CHECK(exp, act)                                                        \\
  if (exp != act) {                                                            \\
    DUMPLN(exp);                                                               \\
    DEBUGLN(act);                                                              \\
  }
#define STOP(e)                                                                \\
  CHECK(e, true);                                                              \\
  if (!(e))                                                                    \\
    exit(1);
#endif

template <class T> inline string toString(const vector<T> &x) {
  stringstream ss;
  REP(i, x.size()) {
    if (i != 0)
      ss << " ";
    ss << x[i];
  }
  return ss.str();
}

template <class T> inline string toString(const vector<vector<T>> &map) {
  stringstream ss;
  REP(i, map.size()) {
    if (i != 0)
      ss << BR;
    ss << toString(map[i]);
  }
  return ss.str();
}
template <class K, class V> string toString(map<K, V> &x) {
  string res;
  stringstream ss;
  for (auto &p : x)
    ss << p.first << ":" << p.second << " ";
  return ss.str();
}

string BITtoString(int bit) {
  stringstream ss;
  while (bit != 0) {
    ss << (bit % 2);
    bit /= 2;
  }
  string res = ss.str();
  reverse(ALL(res));
  return res;
}

template <typename T, typename V> inline T pmod(T v, V MOD) {
  return (v % MOD + MOD) % MOD;
}

class Main {
public:
  void run() {
    while (true) {
      int N;
      cin >> N;
      if (N == 0)
        break;
      vector<int> hs(N + 1);
      REP(i, N + 1) cin >> hs[i];

      for (int e = 0; e < N + 1; e++) {
        vector<int> ts(N);
        int j = 0;
        for (int i = 0; i < N + 1; i++)
          if (i != e)
            ts[j++] = hs[i];

        bool ok = true;
        int d = ts[1] - ts[0];
        for (int i = 1; i < N; i++)
          if (d != ts[i] - ts[i - 1])
            ok = false;
        if (ok) {
          cout << hs[e] << endl;
          break;
        }
      }
    }
  }
};

int main() {
  // ios::sync_with_stdio(false);
  Main().run();
  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <complex>
#include <cstdio>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

// common
typedef long long i64, ll;

#define BR "\\n"
#define ALL(c) (c).begin(), (c).end()
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define FOR(i, l, r) for (int i = (l); i < (int)(r); ++i)
#define EACH(it, o) for (auto it = (o).begin(); it != (o).end(); ++it)
#define IN(l, v, r) ((l) <= (v) && (v) < (r))

// debug
#ifdef NDEBUG
#define DUMP(x)
#define DUMPLN(x)
#define DEBUG(x)
#define DEBUGLN(x)
#define LINE()
#define LINELN()
#define CHECK(exp, act)
#define STOP(e)
#else
#define DUMP(x) cerr << #x << " = " << (x)
#define DUMPLN(x) DUMP(x) << endl
#define DEBUG(x) DUMP(x) << LINE() << " " << __FILE__
#define DEBUGLN(x) DEBUG(x) << endl
#define LINE() cerr << " (L" << __LINE__ << ")"
#define LINELN() LINE() << endl
#define CHECK(exp, act)                                                        \\
  if (exp != act) {                                                            \\
    DUMPLN(exp);                                                               \\
    DEBUGLN(act);                                                              \\
  }
#define STOP(e)                                                                \\
  CHECK(e, true);                                                              \\
  if (!(e))                                                                    \\
    exit(1);
#endif

template <class T> inline string toString(const vector<T> &x) {
  stringstream ss;
  REP(i, x.size()) {
    if (i != 0)
      ss << " ";
    ss << x[i];
  }
  return ss.str();
}

template <class T> inline string toString(const vector<vector<T>> &map) {
  stringstream ss;
  REP(i, map.size()) {
    if (i != 0)
      ss << BR;
    ss << toString(map[i]);
  }
  return ss.str();
}
template <class K, class V> string toString(map<K, V> &x) {
  string res;
  stringstream ss;
  for (auto &p : x)
    ss << p.first << ":" << p.second << " ";
  return ss.str();
}

string BITtoString(int bit) {
  stringstream ss;
  while (bit != 0) {
    ss << (bit % 2);
    bit /= 2;
  }
  string res = ss.str();
  reverse(ALL(res));
  return res;
}

template <typename T, typename V> inline T pmod(T v, V MOD) {
  return (v % MOD + MOD) % MOD;
}

class Main {
public:
  void run() {
    while (true) {
      int N;
      cin >> N;
      vector<int> hs(N + 1);
      REP(i, N + 1) cin >> hs[i];

      for (int e = 0; e < N + 1; e++) {
        int d = -1;
        int pv = -1;
        bool ok = true;
        for (int i = 0; i < N + 1; i++)
          if (i != e) {
            if (pv == -1) { // 1
              pv = hs[i];
              continue;
            }
            if (d == -1) { // 2
              d = hs[i] - pv;
              pv = hs[i];
              continue;
            }
            if (d == hs[i] - pv) { // 2<
              pv = hs[i];
              continue;
            } else {
              ok = false;
              break;
            }
          }
        if (ok) {
          cout << hs[e] << endl;
          break;
        }
      }
    }
  }
};

int main() {
  // ios::sync_with_stdio(false);
  Main().run();
  return 0;
}