Problem p02623 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>

#define debug(x)                                                               \\
  cout << "DEBUG"                                                              \\
       << " " << #x << ":" << x << '\\n'
#define rep(i, n)                                                              \\
  for (int_fast32_t i = 0; i < ((int_fast32_t)(n)); i++) // 0-indexed up
#define rep1(i, n)                                                             \\
  for (int_fast32_t i = 1; i <= ((int_fast32_t)(n)); i++) // 1-indexed up
#define rrep(i, n)                                                             \\
  for (int_fast32_t i = ((int_fast32_t)(n)-1); i >= 0; i--) // 0-indexed down
#define rrep1(i, n)                                                            \\
  for (int_fast32_t i = ((int_fast32_t)(n)); i >= 1; i--) // 1-indexed down
#define all(x) (x).begin(), (x).end()

using namespace std;

template <typename T> using vec = vector<T>;
using i32 = int_fast32_t;
using i64 = int_fast64_t;
using u32 = uint_fast32_t;
using u64 = uint_fast64_t;
using ll = long long;
using ld = long double;
using vi = vec<int_fast32_t>;
using vl = vec<int_fast64_t>;
using vld = vec<ld>;
using vii = vec<vi>;
using PII = pair<int_fast32_t, int_fast32_t>;

template <class T> using maxheap = std::priority_queue<T>;
template <class T>
using minheap = std::priority_queue<T, std::vector<T>, std::greater<T>>;

template <class T, class U> inline bool chmax(T &a, const U &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T, class U> inline bool chmin(T &a, const U &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

const ld Pi = std::acos(-1.0L);
constexpr ll infll = (1LL << 62) - 1;
constexpr int inf = (1 << 30) - 1;
const int mod = 1000000007;
// const int mod = 998244353;

/*FUNCs=================================================*/

/*MAIN==================================================*/
signed main() {
  int START_TIME = clock();
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  //    cout << fixed << setprecision(15);

  i64 n, m, k;
  cin >> n >> m >> k;
  vl a_csum(n + 1), b_csum(m);
  rep1(i, n) cin >> a_csum[i];
  rep(i, m) cin >> b_csum[i];
  for (i32 i = 0; i < n; ++i)
    a_csum[i + 1] += a_csum[i];
  for (i32 i = 1; i < m; ++i)
    b_csum[i] += b_csum[i - 1];
  //
  //    rep(i,n) cout << a_csum[i] << ' '; cout << '\\n';
  //    rep(i,m) cout << b_csum[i] << ' '; cout << '\\n';

  i32 ans = 0;
  for (i32 i = 0; i <= n; ++i) {
    i64 sum = k - a_csum[i];
    if (sum < 0)
      break;
    i32 idx = upper_bound(all(b_csum), sum) - b_csum.begin();
    //        debug(i);
    //        debug(a_csum[i]);
    //        debug(sum);
    //        debug(idx);
    //        debug(upper_bound(all(b_csum), 310) - b_csum.begin());
    chmax(ans, i + idx);
  }

  cout << ans << '\\n';

  // printf("ExecutionTime: %d
  // /ms\\n",1000*(int)((clock()-START_TIME)/CLOCKS_PER_SEC));
}


Error: WA

Fixed submission:

#include <bits/stdc++.h>

#define debug(x)                                                               \\
  cout << "DEBUG"                                                              \\
       << " " << #x << ":" << x << '\\n'
#define rep(i, n)                                                              \\
  for (int_fast32_t i = 0; i < ((int_fast32_t)(n)); i++) // 0-indexed up
#define rep1(i, n)                                                             \\
  for (int_fast32_t i = 1; i <= ((int_fast32_t)(n)); i++) // 1-indexed up
#define rrep(i, n)                                                             \\
  for (int_fast32_t i = ((int_fast32_t)(n)-1); i >= 0; i--) // 0-indexed down
#define rrep1(i, n)                                                            \\
  for (int_fast32_t i = ((int_fast32_t)(n)); i >= 1; i--) // 1-indexed down
#define all(x) (x).begin(), (x).end()

using namespace std;

template <typename T> using vec = vector<T>;
using i32 = int_fast32_t;
using i64 = int_fast64_t;
using u32 = uint_fast32_t;
using u64 = uint_fast64_t;
using ll = long long;
using ld = long double;
using vi = vec<int_fast32_t>;
using vl = vec<int_fast64_t>;
using vld = vec<ld>;
using vii = vec<vi>;
using PII = pair<int_fast32_t, int_fast32_t>;

template <class T> using maxheap = std::priority_queue<T>;
template <class T>
using minheap = std::priority_queue<T, std::vector<T>, std::greater<T>>;

template <class T, class U> inline bool chmax(T &a, const U &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T, class U> inline bool chmin(T &a, const U &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

const ld Pi = std::acos(-1.0L);
constexpr ll infll = (1LL << 62) - 1;
constexpr int inf = (1 << 30) - 1;
const int mod = 1000000007;
// const int mod = 998244353;

/*FUNCs=================================================*/

/*MAIN==================================================*/
signed main() {
  int START_TIME = clock();
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  //    cout << fixed << setprecision(15);

  i32 n, m, k, tmp;
  cin >> n >> m >> k;
  vl a_csum(n), b_csum(m);
  rep(i, n) cin >> a_csum[i];
  rep(i, m) cin >> b_csum[i];
  for (i32 i = 1; i < n; ++i)
    a_csum[i] += a_csum[i - 1];
  for (i32 i = 1; i < n; ++i)
    b_csum[i] += b_csum[i - 1];

  rep(i, n) cout << a_csum[i] << ' ';
  cout << '\\n';
  rep(i, m) cout << b_csum[i] << ' ';
  cout << '\\n';

  i32 ans = 0;
  for (i32 i = 0; i < n; ++i) {
    i64 sum = k - a_csum[i];
    if (sum < 0)
      break;
    i32 idx = min(m, upper_bound(all(b_csum), sum) - b_csum.begin());
    debug(i);
    debug(a_csum[i]);
    debug(sum);
    debug(idx);
    chmax(ans, i + 1 + idx);
  }

  cout << ans << '\\n';

  // printf("ExecutionTime: %d
  // /ms\\n",1000*(int)((clock()-START_TIME)/CLOCKS_PER_SEC));
}