Problem p00188 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>
using namespace std;

// #define int long long
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;

#define rep(i, a, b) for (int i = (a); i < (b); i++)
#define rrep(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define all(a) (a).begin(), (a).end()
#define dump(o)                                                                \
  { cerr << #o << " " << o << endl; }
#define dumpc(o)                                                               \
  {                                                                            \
    cerr << #o;                                                                \
    for (auto &e : (o))                                                        \
      cerr << " " << e;                                                        \
    cerr << endl;                                                              \
  }
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
const int MOD = 1e9 + 7;

signed main() {
  for (int n; cin >> n && n;) {
    vector<int> a(n);
    rep(i, 0, n) cin >> a[i];
    int s;
    cin >> s;
    int l = 0, r = n - 1;
    int cnt = 0;
    while (true) {
      cnt++;
      if (r - l == 0)
        break;
      int m = (l + r) / 2;
      // dump(m); dump(l); dump(r);
      if (a[m] > s)
        r = m - 1;
      else if (a[m] < s)
        l = m + 1;
      else
        break;
    }
    cout << cnt << endl;
  }
  return 0;
}

Fixed submission:
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>
using namespace std;

// #define int long long
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;

#define rep(i, a, b) for (int i = (a); i < (b); i++)
#define rrep(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define all(a) (a).begin(), (a).end()
#define dump(o)                                                                \
  { cerr << #o << " " << o << endl; }
#define dumpc(o)                                                               \
  {                                                                            \
    cerr << #o;                                                                \
    for (auto &e : (o))                                                        \
      cerr << " " << e;                                                        \
    cerr << endl;                                                              \
  }
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
const int MOD = 1e9 + 7;

signed main() {
  for (int n; cin >> n && n;) {
    vector<int> a(n);
    rep(i, 0, n) cin >> a[i];
    int s;
    cin >> s;
    int l = 0, r = n - 1;
    int cnt = 0;
    while (true) {
      if (r - l < 0)
        break;
      cnt++;
      if (r - l == 0)
        break;
      int m = (l + r) / 2;
      // dump(m); dump(l); dump(r);
      if (a[m] > s)
        r = m - 1;
      else if (a[m] < s)
        l = m + 1;
      else
        break;
    }
    cout << cnt << endl;
  }
  return 0;
}