Problem p02726 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

#define sqr(x) ((x) * (x))
#define mp make_pair
#define pb push_back
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define RE(i, n) FOR(i, 1, n)
#define REP(i, n) FOR(i, 0, (int)(n)-1)
#define fst first
#define snd second

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, int> pli;
typedef pair<ll, ll> pll;
typedef long double ld;
typedef tuple<int, int, int> iii;

string to_string(string s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

void debug_out() { cerr << endl; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

void fastIO() {
  cin.sync_with_stdio(false);
  cin.tie(0);
}

int XMOV[4] = {0, 0, 1, -1};
int YMOV[4] = {1, -1, 0, 0};

// #############################
const int MAXN = 1000005;

int main() {
  vector<int> g[1005];
  int n, x, y;
  cin >> n >> x >> y;

  for (int i = 1; i < n; i++) {
    g[i].pb(i + 1);
    g[i + 1].pb(i);
  }

  g[x].pb(y);
  g[y].pb(x);

  ll ans[2005];
  memset(ans, 0, sizeof(ans));
  bool mark[2005];
  queue<pii> q;
  for (int node = 1; node <= n; node++) {
    q.push(pii(node, 0));
    // cout << "node: " << node << endl;
    memset(mark, 0, sizeof(mark));
    mark[node] = true;
    while (!q.empty()) {
      int j = q.front().snd;
      // for(int i = 0; i < q.size(); i++){
      //     cout << q.front().fst << " ";
      //     q.push(q.front());
      //     q.pop();
      // }
      // cout << endl;
      int src = q.front().fst;
      q.pop();

      for (auto w : g[src]) {
        if (!mark[w]) {
          mark[w] = true;
          ans[j + 1]++;
          q.push(pii(w, j + 1));
        }
      }
    }
  }
  int i = 1;
  // cout << "---" << endl;
  while (i < n) {
    cout << ans[i] / 2 << endl;
    i++;
  }

  return 0;
}

Fixed submission:
#include <algorithm>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

#define sqr(x) ((x) * (x))
#define mp make_pair
#define pb push_back
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define RE(i, n) FOR(i, 1, n)
#define REP(i, n) FOR(i, 0, (int)(n)-1)
#define fst first
#define snd second

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, int> pli;
typedef pair<ll, ll> pll;
typedef long double ld;
typedef tuple<int, int, int> iii;

string to_string(string s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

void debug_out() { cerr << endl; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

void fastIO() {
  cin.sync_with_stdio(false);
  cin.tie(0);
}

int XMOV[4] = {0, 0, 1, -1};
int YMOV[4] = {1, -1, 0, 0};

// #############################
const int MAXN = 1000005;

int main() {
  vector<int> g[2005];
  int n, x, y;
  cin >> n >> x >> y;

  for (int i = 1; i < n; i++) {
    g[i].pb(i + 1);
    g[i + 1].pb(i);
  }

  g[x].pb(y);
  g[y].pb(x);

  ll ans[2005];
  memset(ans, 0, sizeof(ans));
  bool mark[2005];
  queue<pii> q;
  for (int node = 1; node <= n; node++) {
    q.push(pii(node, 0));
    // cout << "node: " << node << endl;
    memset(mark, 0, sizeof(mark));
    mark[node] = true;
    while (!q.empty()) {
      int j = q.front().snd;
      // for(int i = 0; i < q.size(); i++){
      //     cout << q.front().fst << " ";
      //     q.push(q.front());
      //     q.pop();
      // }
      // cout << endl;
      int src = q.front().fst;
      q.pop();

      for (auto w : g[src]) {
        if (!mark[w]) {
          mark[w] = true;
          ans[j + 1]++;
          q.push(pii(w, j + 1));
        }
      }
    }
  }
  int i = 1;
  // cout << "---" << endl;
  while (i < n) {
    cout << ans[i] / 2 << endl;
    i++;
  }

  return 0;
}