Problem p01111 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
    cout.precision(20);
  }
} fast;

/* define */
#define FOR(I, X, Y) for (long long(I) = (X); (I) < (Y); (I)++)
#define REP(I, X, Y) for (long long(I) = (Y)-1; (I) >= (X); (I)--)
#define ALL(X) (X).begin(), (X).end()
#define pb push_back
#define COUNT(V, X)                                                            \\
  (upper_bound((V).begin(), (V).end(), X) -                                    \\
   lower_bound((V).begin(), (V).end(), X))
#define debug(x) cerr << #x << ':' << x << endl;
#define DEBUG(v)                                                               \\
  {                                                                            \\
    cerr << #v << ':';                                                         \\
    for (auto xv : v)                                                          \\
      cerr << xv << ' ';                                                       \\
    cerr << endl;                                                              \\
  }
#define Yes(X) cout << (X ? "Yes" : "No") << endl;
#define YES(X) cout << (X ? "YES" : "NO") << endl;
#define ctoi(C) (C - '0')
#define pow2(x) ((long long)((long long)1 << x))

/* alias */
using ll = long long;
using ld = long double;
using vi = vector<int>;
using vii = vector<vector<int>>;
using vl = vector<long long>;
using vll = vector<vector<long long>>;
using pi = pair<int, int>;
using pl = pair<long long, long long>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const long long dx[] = {1, 0, -1, 0};
const long long dy[] = {0, 1, 0, -1};
const long long dx8[] = {1, 1, 0, -1, -1, -1, 0, 1};
const long long dy8[] = {0, 1, 1, 1, 0, -1, -1, -1};
const long long dx9[] = {1, 1, 0, -1, -1, -1, 0, 1, 0};
const long long dy9[] = {0, 1, 1, 1, 0, -1, -1, -1, 0};
const int INF = 1000000007;
const long long LINF = 1000000000000000007;

/* func */
template <typename T> inline bool chmin(T &a, const T &b) {
  if (a > b)
    a = b;
  return a > b;
}
template <typename T> inline bool chmax(T &a, const T &b) {
  if (a < b)
    a = b;
  return a < b;
}
long long max(long long x, int y) { return max(x, (long long)y); }
long long max(int x, long long y) { return max((long long)x, y); }
long long min(long long x, int y) { return min(x, (long long)y); }
long long min(int x, long long y) { return min((long long)x, y); }

/* liblary */

/* main */

bool check(ll &imid, ll &b, ll &i) {
  ll m = i + imid - 1;
  ll n = imid - 1;
  return m * (m + 1) / 2 - n * (n + 1) / 2 >= b;
}

bool check2(ll &imid, ll &b, ll &i) {
  ll m = i + imid - 1;
  ll n = imid - 1;
  return m * (m + 1) / 2 - n * (n + 1) / 2 == b;
}

void solve(ll b) {
  REP(i, 1, 50000) {
    ll imax = INF;
    ll imin = 0;
    while (imax - imin > 1) {
      ll imid = (imax + imin) / 2;
      if (check(imid, b, i))
        imax = imid;
      else
        imin = imid;
    }
    if (check2(imax, b, i)) {
      cout << imax << ' ' << i << endl;
      return;
    }
  }
}

signed main() {
  ll b;
  while (cin >> b) {
    if (b == 0)
      return 0;
    solve(b);
  }
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
    cout.precision(20);
  }
} fast;

/* define */
#define FOR(I, X, Y) for (long long(I) = (X); (I) < (Y); (I)++)
#define REP(I, X, Y) for (long long(I) = (Y)-1; (I) >= (X); (I)--)
#define ALL(X) (X).begin(), (X).end()
#define pb push_back
#define COUNT(V, X)                                                            \\
  (upper_bound((V).begin(), (V).end(), X) -                                    \\
   lower_bound((V).begin(), (V).end(), X))
#define debug(x) cerr << #x << ':' << x << endl;
#define DEBUG(v)                                                               \\
  {                                                                            \\
    cerr << #v << ':';                                                         \\
    for (auto xv : v)                                                          \\
      cerr << xv << ' ';                                                       \\
    cerr << endl;                                                              \\
  }
#define Yes(X) cout << (X ? "Yes" : "No") << endl;
#define YES(X) cout << (X ? "YES" : "NO") << endl;
#define ctoi(C) (C - '0')
#define pow2(x) ((long long)((long long)1 << x))

/* alias */
using ll = long long;
using ld = long double;
using vi = vector<int>;
using vii = vector<vector<int>>;
using vl = vector<long long>;
using vll = vector<vector<long long>>;
using pi = pair<int, int>;
using pl = pair<long long, long long>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const long long dx[] = {1, 0, -1, 0};
const long long dy[] = {0, 1, 0, -1};
const long long dx8[] = {1, 1, 0, -1, -1, -1, 0, 1};
const long long dy8[] = {0, 1, 1, 1, 0, -1, -1, -1};
const long long dx9[] = {1, 1, 0, -1, -1, -1, 0, 1, 0};
const long long dy9[] = {0, 1, 1, 1, 0, -1, -1, -1, 0};
const int INF = 1000000007;
const long long LINF = 1000000000000000007;

/* func */
template <typename T> inline bool chmin(T &a, const T &b) {
  if (a > b)
    a = b;
  return a > b;
}
template <typename T> inline bool chmax(T &a, const T &b) {
  if (a < b)
    a = b;
  return a < b;
}
long long max(long long x, int y) { return max(x, (long long)y); }
long long max(int x, long long y) { return max((long long)x, y); }
long long min(long long x, int y) { return min(x, (long long)y); }
long long min(int x, long long y) { return min((long long)x, y); }

/* liblary */

/* main */

bool check(ll &imid, ll &b, ll &i) {
  ll m = i + imid - 1;
  ll n = imid - 1;
  return m * (m + 1) / 2 - n * (n + 1) / 2 >= b;
}

bool check2(ll &imid, ll &b, ll &i) {
  ll m = i + imid - 1;
  ll n = imid - 1;
  return m * (m + 1) / 2 - n * (n + 1) / 2 == b;
}

void solve(ll b) {
  REP(i, 1, 100000) {
    ll imax = INF;
    ll imin = 0;
    while (imax - imin > 1) {
      ll imid = (imax + imin) / 2;
      if (check(imid, b, i))
        imax = imid;
      else
        imin = imid;
    }
    if (check2(imax, b, i)) {
      cout << imax << ' ' << i << endl;
      return;
    }
  }
}

signed main() {
  ll b;
  while (cin >> b) {
    if (b == 0)
      return 0;
    solve(b);
  }
}