Problem p02696 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
typedef long long ll;
const ll MOD = 1e9 + 7;

#define REP(i, N) for (ll i = 0; i < (N); i++)
#define REPP(i, a, b) for (ll i = (a); i < (b); i++)
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
#define VSORT(c) sort((c).begin(), (c).end())
#define SZ(x) ((ll)(x).size())
// vvintを作る　マクロで　 #define vvint(N,M) vector<vector<ll>>

using namespace std;
// 変数初期化
vector<ll> bsv; // binary_search用のvector
ll a, b, c, n, m;
typedef pair<ll, ll> Pll;
vector<Pll> facts; // 素因数分解の結果格納用(基数:乗数)
vector<vector<ll>> bit_search_v; // nit全探索の結果格納用

// index が条件を満たすかどうか
bool isOK(ll index, ll key) {
  if (bsv[index] >= key)
    return true;
  else
    return false;
}

// 汎用的な二分探索のテンプレ
ll binary_search(int key) {
  int ng = -1;
  int ok = (ll)bsv.size();

  /* ok と ng のどちらが大きいかわからないことを考慮 */
  while (abs(ok - ng) > 1) {
    int mid = (ok + ng) / 2;

    if (isOK(mid, key))
      ok = mid;
    else
      ng = mid;
  }
  // OK(key以上となる)のindex番号を返す
  return ok;
}

// 最大公約数
int gcd(int a, int b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}

// 最小公倍数
int lcm(int a, int b) { return a * b / gcd(a, b); }

// 　素因数分解
void prime_fact(ll target) {
  ll base = 2, exp = 0;
  while (base * base <= target) {
    while (target % base == 0) {
      target /= base;
      exp++;
    }
    if (exp > 0) {
      facts.push_back(make_pair(base, exp));
    }
    base++;
    exp = 0;
  }
  if (target > 1)
    facts.push_back(make_pair(target, 1));
}
// prime_factの結果の確認用
void print_facts() {
  for (int i = 0; i < facts.size(); i++) {
    cout << facts[i].first << " " << facts[i].second << endl;
  }
}

// bit全探索
void bit_search(ll target) {
  for (ll i = 0; i < (1 << target); ++i) {
    if (i == 0)
      continue;
    vector<ll> v;
    for (ll j = 0; j < target; ++j) {
      if (i & (1 << j))
        v.push_back(j);
      if (i & (1 << j))
        cout << i << "  :  " << j << endl;
    }
    bit_search_v.push_back(v);
  }
}
// bit全探索の結果確認用
void print_bit_search() {
  for (ll i = 0; i < bit_search_v.size(); ++i) {
    for (ll j = 0; j < bit_search_v[i].size(); ++j) {
      cout << bit_search_v[i][j] << " ";
    }
    cout << endl;
  }
}

int main() {

  cin.tie(0);
  ios::sync_with_stdio(false);

  cin >> a >> b >> n;

  ll x = n;
  if (x >= b) {
    cout << (a * (b - 1)) / b << endl;
  } else {
    cout << (a * x) / b << endl;
  }

  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
typedef long long ll;
const ll MOD = 1e9 + 7;

#define REP(i, N) for (ll i = 0; i < (N); i++)
#define REPP(i, a, b) for (ll i = (a); i < (b); i++)
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
#define VSORT(c) sort((c).begin(), (c).end())
#define SZ(x) ((ll)(x).size())
// vvintを作る　マクロで　 #define vvint(N,M) vector<vector<ll>>

using namespace std;
// 変数初期化
vector<ll> bsv; // binary_search用のvector
ll a, b, c, n, m;
typedef pair<ll, ll> Pll;
vector<Pll> facts; // 素因数分解の結果格納用(基数:乗数)
vector<vector<ll>> bit_search_v; // nit全探索の結果格納用

// index が条件を満たすかどうか
bool isOK(ll index, ll key) {
  if (bsv[index] >= key)
    return true;
  else
    return false;
}

// 汎用的な二分探索のテンプレ
ll binary_search(int key) {
  int ng = -1;
  int ok = (ll)bsv.size();

  /* ok と ng のどちらが大きいかわからないことを考慮 */
  while (abs(ok - ng) > 1) {
    int mid = (ok + ng) / 2;

    if (isOK(mid, key))
      ok = mid;
    else
      ng = mid;
  }
  // OK(key以上となる)のindex番号を返す
  return ok;
}

// 最大公約数
int gcd(int a, int b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}

// 最小公倍数
int lcm(int a, int b) { return a * b / gcd(a, b); }

// 　素因数分解
void prime_fact(ll target) {
  ll base = 2, exp = 0;
  while (base * base <= target) {
    while (target % base == 0) {
      target /= base;
      exp++;
    }
    if (exp > 0) {
      facts.push_back(make_pair(base, exp));
    }
    base++;
    exp = 0;
  }
  if (target > 1)
    facts.push_back(make_pair(target, 1));
}
// prime_factの結果の確認用
void print_facts() {
  for (int i = 0; i < facts.size(); i++) {
    cout << facts[i].first << " " << facts[i].second << endl;
  }
}

// bit全探索
void bit_search(ll target) {
  for (ll i = 0; i < (1 << target); ++i) {
    if (i == 0)
      continue;
    vector<ll> v;
    for (ll j = 0; j < target; ++j) {
      if (i & (1 << j))
        v.push_back(j);
      if (i & (1 << j))
        cout << i << "  :  " << j << endl;
    }
    bit_search_v.push_back(v);
  }
}
// bit全探索の結果確認用
void print_bit_search() {
  for (ll i = 0; i < bit_search_v.size(); ++i) {
    for (ll j = 0; j < bit_search_v[i].size(); ++j) {
      cout << bit_search_v[i][j] << " ";
    }
    cout << endl;
  }
}

int main() {

  cin.tie(0);
  ios::sync_with_stdio(false);

  cin >> a >> b >> n;

  ll x = n, o;
  for (ll i = n; i > 0; i--) {
    if (i % b == 0) {
      x = i - 1;
      break;
    }
  }
  cout << floor((a * x) / b) - a * floor(x / b) << endl;

  return 0;
}