Problem p02696 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
#define REP(i, x, n) for (int i = x; i < (int)n; i++)
#define rep(i, n) REP(i, 0, n)
#define sp(p) cout << setprecision(16) << fixed << p << endl;
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define SORT(a) sort(all(a))
#define RSORT(a) sort(rall(a))
#define UNIQ(a) unique(all(a))
#define UNIQNUM(a) UNIQ(a) - a.begin()
#define UNIQIT(a) a.erase(UNIQ(a), a.end());
#define VOUT(v, i)                                                             \
  rep(i, v.size()) cout << v[i] << (i == v.size() - 1 ? "\n" : " ");
#define vout(v) VOUT(v, z);
#define vdbg(v, i)                                                             \
  cout << #v << ": ";                                                          \
  for (int i = 0; i < (int)v.size(); i++) {                                    \
    cout << v[i] << " ";                                                       \
  }                                                                            \
  cout << "\n";
#define vmin(v) *min_element(all(v))
#define vmax(v) *max_element(all(v))
#define vsum(v) accumulate(all(v), 0LL)
#define MOUT(m, r, c)                                                          \
  rep(i, r) {                                                                  \
    rep(j, c) { cout << m[i][j] << " "; }                                      \
    cout << endl;                                                              \
  }
#define mout(m) MOUT(m, m.size(), m[0].size())
#define debg(a) cout << #a << ": " << a << endl;
#define show(a)                                                                \
  for (cont & y : a) {                                                         \
    for (cont & x : y) {                                                       \
      cout << x << " ";                                                        \
    }                                                                          \
    cout << endl;                                                              \
  }
#define digit(a) to_string(a).length();
template <class T> inline int out(const T &t) {
  print(t);
  putchar('\n');
  return 0;
}
// template<class T>inline T gcd(T a,T b){if(b==0)return a; return(gcd(b,a%b));}
// template<class T>inline T lcm(T a,T b){return a/gcd(a,b)*b;}
bool is_palindrome(string s) { return s == string(s.rbegin(), s.rend()); }
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef vector<vector<ll>> VV;
// const long long MOD=1000000007;
const long long INF = 1e18;
#define EPS (1e-7)
#define PI (acos(-1))
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

// bool check(ll mid){

// }

int main() {
  long long A;
  scanf("%lld", &A);
  long long B;
  scanf("%lld", &B);
  long long N;
  scanf("%lld", &N);
  // solve(A, B, N);

  // ll ng=-1, ok=N;
  // while(abs(ok-ng)>1){
  //     int mid=(ok+ng)/2;
  //     if(check(mid)){
  //         ok=mid;
  //     }else{
  //         ng=mid;
  //     }
  // }

  ll ma = 0;

  if (B - 1 <= N) {
    ll b = B - 1;
    cout << floor(A * b * 1.0 / B) - A * floor(b * 1.0 / B) << endl;
    return 0;
  }

  if (N <= 10e7) {
    for (long long i = 0; i <= N; i++) {
      ll v = floor(A * i * 1.0 / B) - A * floor(i * 1.0 / B);
      // cout << v << endl;
      ma = max(ma, v);
    }
  } else {
    for (long long i = 0; i <= 10e8; i++) {
      ll v = floor(A * i * 1.0 / B) - A * floor(i * 1.0 / B);
      // cout << v << endl;
      ma = max(ma, v);
    }
  }

  // ll b = B-1;
  // ma = floor(A*b*1.0/B) - A*floor(b*1.0/B);

  cout << ma << endl;

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define REP(i, x, n) for (int i = x; i < (int)n; i++)
#define rep(i, n) REP(i, 0, n)
#define sp(p) cout << setprecision(16) << fixed << p << endl;
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define SORT(a) sort(all(a))
#define RSORT(a) sort(rall(a))
#define UNIQ(a) unique(all(a))
#define UNIQNUM(a) UNIQ(a) - a.begin()
#define UNIQIT(a) a.erase(UNIQ(a), a.end());
#define VOUT(v, i)                                                             \
  rep(i, v.size()) cout << v[i] << (i == v.size() - 1 ? "\n" : " ");
#define vout(v) VOUT(v, z);
#define vdbg(v, i)                                                             \
  cout << #v << ": ";                                                          \
  for (int i = 0; i < (int)v.size(); i++) {                                    \
    cout << v[i] << " ";                                                       \
  }                                                                            \
  cout << "\n";
#define vmin(v) *min_element(all(v))
#define vmax(v) *max_element(all(v))
#define vsum(v) accumulate(all(v), 0LL)
#define MOUT(m, r, c)                                                          \
  rep(i, r) {                                                                  \
    rep(j, c) { cout << m[i][j] << " "; }                                      \
    cout << endl;                                                              \
  }
#define mout(m) MOUT(m, m.size(), m[0].size())
#define debg(a) cout << #a << ": " << a << endl;
#define show(a)                                                                \
  for (cont & y : a) {                                                         \
    for (cont & x : y) {                                                       \
      cout << x << " ";                                                        \
    }                                                                          \
    cout << endl;                                                              \
  }
#define digit(a) to_string(a).length();
template <class T> inline int out(const T &t) {
  print(t);
  putchar('\n');
  return 0;
}
// template<class T>inline T gcd(T a,T b){if(b==0)return a; return(gcd(b,a%b));}
// template<class T>inline T lcm(T a,T b){return a/gcd(a,b)*b;}
bool is_palindrome(string s) { return s == string(s.rbegin(), s.rend()); }
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef vector<vector<ll>> VV;
// const long long MOD=1000000007;
const long long INF = 1e18;
#define EPS (1e-7)
#define PI (acos(-1))
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

// bool check(ll mid){

// }

int main() {
  long long A;
  scanf("%lld", &A);
  long long B;
  scanf("%lld", &B);
  long long N;
  scanf("%lld", &N);
  // solve(A, B, N);

  // ll ng=-1, ok=N;
  // while(abs(ok-ng)>1){
  //     int mid=(ok+ng)/2;
  //     if(check(mid)){
  //         ok=mid;
  //     }else{
  //         ng=mid;
  //     }
  // }

  ll ma = 0;

  if (B - 1 <= N) {
    ll b = B - 1;
    cout << floor(A * b * 1.0 / B) - A * floor(b * 1.0 / B) << endl;
    return 0;
  }

  if (N <= 10e7) {
    for (long long i = 0; i <= N; i++) {
      ll v = floor(A * i * 1.0 / B) - A * floor(i * 1.0 / B);
      // cout << v << endl;
      ma = max(ma, v);
    }
  } else {
    for (long long i = N; N - i <= 10e7; i--) {
      ll v = floor(A * i * 1.0 / B) - A * floor(i * 1.0 / B);
      // cout << v << endl;
      ma = max(ma, v);
    }
  }

  // ll b = B-1;
  // ma = floor(A*b*1.0/B) - A*floor(b*1.0/B);

  cout << ma << endl;

  return 0;
}