Problem p02603 (C++)

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

using namespace std;
typedef long long ll;

#define MOD (long long)(1e9 + 7)
#define INF (1LL << 60)
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define rep1(i, n) for (ll i = 1; i <= (n); i++)

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

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

// mod m におけるa の逆元
ll modinv(ll a, ll m) {
  ll b = m, u = 1, v = 0;
  while (b) {
    ll t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0)
    u += m;
  return u;
}

// 素因数分解
vector<pair<ll, ll>> prim;
void pf(ll n) {
  ll s = sqrt(n);
  ll r = 0;
  for (ll i = 2; i <= s; i++) {
    if ((n % i) == 0) {
      r = 0;
      do {
        r++;
        n = n / i;
      } while ((n % i) == 0);
      prim.push_back({i, r});
    }
  }
  if (n > s) {
    prim.push_back({n, 1});
  }
}

void solve() {
  ll N;
  cin >> N;
  // ll N, K; cin >> N >> K;
  // ll x, y, z; cin >> x >> y >> z;
  // ll a, b, c; cin >> a >> b >> c;
  // string s; cin >> s;
  vector<ll> a(N);
  rep(i, N) cin >> a[i];

  ll ans = 1000;
  ll kabu = 0;
  ll day = 0;
  while (day < N - 1) {

    if (a[day] < a[day + 1]) {

      kabu = ans / a[day];
      ans = ans % a[day];
      day++;
      while (day < N - 1 && a[day] <= a[day + 1]) {
        day++;
      }
    } else if (a[day] > a[day + 1]) {

      ans += kabu * a[day];
      kabu = 0;
      day++;
      while (day < N - 1 && a[day] >= a[day + 1]) {
        day++;
      }
    }
  }
  ans += kabu * a[N - 1];

  cout << ans << endl;
}

int main(void) {
  // ll t; cin >> t; rep(i, t)
  solve();
}


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

using namespace std;
typedef long long ll;

#define MOD (long long)(1e9 + 7)
#define INF (1LL << 60)
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define rep1(i, n) for (ll i = 1; i <= (n); i++)

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

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

// mod m におけるa の逆元
ll modinv(ll a, ll m) {
  ll b = m, u = 1, v = 0;
  while (b) {
    ll t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0)
    u += m;
  return u;
}

// 素因数分解
vector<pair<ll, ll>> prim;
void pf(ll n) {
  ll s = sqrt(n);
  ll r = 0;
  for (ll i = 2; i <= s; i++) {
    if ((n % i) == 0) {
      r = 0;
      do {
        r++;
        n = n / i;
      } while ((n % i) == 0);
      prim.push_back({i, r});
    }
  }
  if (n > s) {
    prim.push_back({n, 1});
  }
}

void solve() {
  ll N;
  cin >> N;
  // ll N, K; cin >> N >> K;
  // ll x, y, z; cin >> x >> y >> z;
  // ll a, b, c; cin >> a >> b >> c;
  // string s; cin >> s;
  vector<ll> a(N);
  rep(i, N) cin >> a[i];

  ll ans = 1000;
  ll kabu = 0;
  ll day = 0;
  while (day < N - 1) {

    if (a[day] < a[day + 1]) {

      kabu = ans / a[day];
      ans = ans % a[day];
      day++;
      while (day < N - 1 && a[day] <= a[day + 1]) {
        day++;
      }
    } else if (a[day] > a[day + 1]) {

      ans += kabu * a[day];
      kabu = 0;
      day++;
      while (day < N - 1 && a[day] >= a[day + 1]) {
        day++;
      }
    } else {
      day++;
    }
  }
  ans += kabu * a[N - 1];

  cout << ans << endl;
}

int main(void) {
  // ll t; cin >> t; rep(i, t)
  solve();
}