Problem p02873 (C++)

Buggy submission (status: Runtime Error):
#pragma GCC target("avx2")
#pragma GCC optimize("O3")

// # include <x86intrin.h>
#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;

template <typename T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define _USE_MATH_DEFINES_
#define ll long long
#define ld long double
#define Accepted 0
#define pb push_back
#define mp make_pair
#define sz(x) (int)(x.size())
#define every(x) x.begin(), x.end()
#define F first
#define S second
#define lb lower_bound
#define ub upper_bound
#define For(i, x, y) for (ll i = x; i <= y; i++)
#define FOr(i, x, y) for (ll i = x; i >= y; i--)
#define SpeedForce ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)
// ROAD to... Red

inline void Input_Output() {
  // freopen(".in", "r", stdin);
  // freopen(".out", "w", stdout);
}

const double eps = 0.000001;
const ld pi = acos(-1);
const int maxn = 1e7 + 9;
const int mod = 1e9 + 7;
const ll MOD = 1e18 + 9;
const ll INF = 1e18 + 123;
const int inf = 2e9 + 11;
const int mxn = 1e6 + 9;
const int N = 6e5 + 123;
const int M = 22;
const int pri = 997;
const int Magic = 2101;

const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, -1, 0, 1};

int n, m, k;
int cnt[N];
string s;
int a[N];
vector<int> g[N];
int u[N];
int ans, res;
int cur;
int was[N];
int deg[N];

int main() {
  SpeedForce;
  cin >> s;
  s = '#' + s;
  n = sz(s);
  for (int i = 1; i < n; i++) {
    if (s[i] == '<')
      g[i].pb(i + 1), u[i + 1] = 1;
    else
      g[i + 1].pb(i), u[i] = 1;
  }

  queue<int> q;
  for (int i = 1; i <= n; i++)
    if (!u[i]) {
      was[i] = 1;
      q.push(i);
    }
  for (int i = 1; i <= n; i++)
    deg[i] = sz(g[i]);

  while (q.size()) {
    int v = q.front();
    q.pop();

    for (auto to : g[v]) {
      deg[to]--;
      if (!deg[to]) {
        was[to] = 1;
        q.push(to);
      }
      a[to] = max(a[to], a[v] + 1);
    }
  }

  cout << accumulate(a + 1, a + n + 1, 0ll);
  return Accepted;
}

// B...a


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

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;

template <typename T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define _USE_MATH_DEFINES_
#define ll long long
#define ld long double
#define Accepted 0
#define pb push_back
#define mp make_pair
#define sz(x) (int)(x.size())
#define every(x) x.begin(), x.end()
#define F first
#define S second
#define lb lower_bound
#define ub upper_bound
#define For(i, x, y) for (ll i = x; i <= y; i++)
#define FOr(i, x, y) for (ll i = x; i >= y; i--)
#define SpeedForce ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)
// ROAD to... Red

inline void Input_Output() {
  // freopen(".in", "r", stdin);
  // freopen(".out", "w", stdout);
}

const double eps = 0.000001;
const ld pi = acos(-1);
const int maxn = 1e7 + 9;
const int mod = 1e9 + 7;
const ll MOD = 1e18 + 9;
const ll INF = 1e18 + 123;
const int inf = 2e9 + 11;
const int mxn = 1e6 + 9;
const int N = 6e5 + 123;
const int M = 22;
const int pri = 997;
const int Magic = 2101;

const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, -1, 0, 1};

int n, m, k;
int cnt[N];
string s;
int a[N];
vector<int> g[N];
int u[N];
int ans, res;
int cur;
int was[N];
int deg[N];

int main() {
  SpeedForce;
  cin >> s;
  s = '#' + s;
  n = sz(s);
  for (int i = 1; i < n; i++) {
    if (s[i] == '<')
      g[i].pb(i + 1), u[i + 1] = 1;
    else
      g[i + 1].pb(i), u[i] = 1;
  }

  queue<int> q;
  for (int i = 1; i <= n; i++)
    if (!u[i]) {
      was[i] = 1;
      q.push(i);
    }
  for (int i = 1; i <= n; i++)
    deg[i] = sz(g[i]);

  while (q.size()) {
    int v = q.front();
    q.pop();

    for (auto to : g[v]) {
      deg[to]--;
      if (!deg[to]) {
        was[to] = 1;
        q.push(to);
      }
      a[to] = max(a[to], a[v] + 1);
    }
  }

  cout << accumulate(a + 1, a + n + 1, 0ll);
  return Accepted;
}

// B...a