Problem p02696 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vint;
typedef vector<double> vdbl;
typedef vector<ll> vll;
typedef vector<string> vstr;
typedef vector<vector<int>> vvint;
typedef vector<pair<int, int>> vpii;
typedef vector<pair<ll, ll>> vpll;
typedef priority_queue<int, vector<int>, greater<int>>
    spqint; // 小さい順に取り出し
typedef priority_queue<ll, vector<ll>, greater<ll>> spqll; // 小さい順に取り出し
typedef priority_queue<int, vector<int>, less<int>> bpqint; // 大きい順に取り出し
typedef priority_queue<ll, vector<ll>, less<ll>> bpqll; // 大きい順に取り出し

#define REP(i, n) for (int(i) = 0; (i) < (int)(n); i++)
#define FOR(i, a, b) for (int(i) = a; (i) < (int)b; i++)
#define IREP(i, v) for (auto i = v.begin(); i != v.end(); i++)
#define MOD 1000000007
#define NIL -1
#define FI first
#define SE second
#define MP make_pair
#define PB push_back
#define PF push_front
#define TS to_string
#define BS binary_search
#define LB lower_bound
#define UB upper_bound
#define NP next_permutation
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) (ll) x.size()
#define SP(x) setprecision((ll)x)

const int INF = 1e9;
const ll LINF = 1e18;
const double EPS = 1e-9;
const double PI = M_PI;
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; } // 最大公約数
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }     // 最小公倍数

void yes() { cout << "Yes" << endl; }
void no() { cout << "No" << endl; }
//-----------------------------------------

//-----------------------------------------
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll a, b, n;
  cin >> a >> b >> n;
  ll ans = 0;
  for (ll i = 0; i <= sqrt(n); i++) {
    ll j = n - i;
    ll k = floor(a * j / b) - a * floor(j / b);
    ans = max(ans, k);
  }
  for (ll i = 0; i <= sqrt(n); i++) {
    ll l = floor(a * i / b) - a * floor(i / b);
    ans = max(ans, l);
  }
  ll bb = b;
  while (1) {
    if (bb >= n) {
      break;
    }
    ll m = floor(a * (bb - 1) / b) - a * floor((bb - 1) / b);
    ans = max(m, ans);
    bb += b;
  }

  cout << ans << endl;

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vint;
typedef vector<double> vdbl;
typedef vector<ll> vll;
typedef vector<string> vstr;
typedef vector<vector<int>> vvint;
typedef vector<pair<int, int>> vpii;
typedef vector<pair<ll, ll>> vpll;
typedef priority_queue<int, vector<int>, greater<int>>
    spqint; // 小さい順に取り出し
typedef priority_queue<ll, vector<ll>, greater<ll>> spqll; // 小さい順に取り出し
typedef priority_queue<int, vector<int>, less<int>> bpqint; // 大きい順に取り出し
typedef priority_queue<ll, vector<ll>, less<ll>> bpqll; // 大きい順に取り出し

#define REP(i, n) for (int(i) = 0; (i) < (int)(n); i++)
#define FOR(i, a, b) for (int(i) = a; (i) < (int)b; i++)
#define IREP(i, v) for (auto i = v.begin(); i != v.end(); i++)
#define MOD 1000000007
#define NIL -1
#define FI first
#define SE second
#define MP make_pair
#define PB push_back
#define PF push_front
#define TS to_string
#define BS binary_search
#define LB lower_bound
#define UB upper_bound
#define NP next_permutation
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) (ll) x.size()
#define SP(x) setprecision((ll)x)

const int INF = 1e9;
const ll LINF = 1e18;
const double EPS = 1e-9;
const double PI = M_PI;
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; } // 最大公約数
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }     // 最小公倍数

void yes() { cout << "Yes" << endl; }
void no() { cout << "No" << endl; }
//-----------------------------------------

//-----------------------------------------
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll a, b, n;
  cin >> a >> b >> n;
  ll ans = 0;
  if (b > n) {
    ans = (a * n) / b - a * (n / b);
  } else {
    ans = (a * (b - 1)) / b;
  }

  cout << ans << endl;

  return 0;
}