Problem p03634 (C++)

Buggy submission (status: Runtime Error):
#include <cassert>

#include <ccomplex>
#include <cctype>
#include <cerrno>
#include <cfenv>
#include <cfloat>
#include <cinttypes>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstdbool>
#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctgmath>
#include <ctime>
#include <cwchar>
#include <cwctype>

// C++
#include <algorithm>
#include <array>
#include <atomic>
#include <bitset>
#include <chrono>
#include <complex>
#include <condition_variable>
#include <deque>
#include <exception>
#include <forward_list>
#include <fstream>
#include <functional>
#include <future>
#include <initializer_list>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <mutex>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <system_error>
#include <thread>
#include <tuple>
#include <type_traits>
#include <typeindex>
#include <typeinfo>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <valarray>
#include <vector>
// #include <boost/foreach.hpp>
// #include <boost/range/algorithm.hpp>
#define rep(i, j, k) for (int i = (int)j; i < (int)k; i++)
#define ll long long
#define Sort(v) sort(all(v))
#define INF 1e9
#define LINF 1e18
#define END return 0
#define pb push_back
#define se second
#define fi first
#define pb push_back
#define all(v) (v).begin(), (v).end()
#define MP make_pair
#define MOD 1000000007LL
#define int long long
using namespace std;
int day[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
struct edge {
  int to, cost;
};
typedef pair<int, int> P;

vector<bool> visit(10010, false);
vector<int> d(10010);
vector<edge> g[10010];

void dfs(int v, int parent, int dist) {
  d[v] = dist;
  rep(i, 0, g[v].size()) {
    edge e = g[v][i];
    if (e.to == parent)
      continue;
    dfs(e.to, v, dist + e.cost);
  }
  return;
}

signed main() {
  int n;
  cin >> n;
  rep(i, 0, n - 1) {
    int a, b, c;
    cin >> a >> b >> c;
    a--;
    b--;
    g[a].push_back({b, c});
    g[b].push_back({a, c});
  }
  int q, k;
  cin >> q >> k;
  k--;
  d[k] = 0;
  dfs(k, -1, 0);

  rep(i, 0, q) {
    int x, y;
    cin >> x >> y;
    x--;
    y--;
    cout << d[x] + d[y] << endl;
  }
}
/*
1-21-2
*/


Fixed submission:
#include <cassert>

#include <ccomplex>
#include <cctype>
#include <cerrno>
#include <cfenv>
#include <cfloat>
#include <cinttypes>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstdbool>
#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctgmath>
#include <ctime>
#include <cwchar>
#include <cwctype>

// C++
#include <algorithm>
#include <array>
#include <atomic>
#include <bitset>
#include <chrono>
#include <complex>
#include <condition_variable>
#include <deque>
#include <exception>
#include <forward_list>
#include <fstream>
#include <functional>
#include <future>
#include <initializer_list>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <mutex>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <system_error>
#include <thread>
#include <tuple>
#include <type_traits>
#include <typeindex>
#include <typeinfo>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <valarray>
#include <vector>
// #include <boost/foreach.hpp>
// #include <boost/range/algorithm.hpp>
#define rep(i, j, k) for (int i = (int)j; i < (int)k; i++)
#define ll long long
#define Sort(v) sort(all(v))
#define INF 1e9
#define LINF 1e18
#define END return 0
#define pb push_back
#define se second
#define fi first
#define pb push_back
#define all(v) (v).begin(), (v).end()
#define MP make_pair
#define MOD 1000000007LL
#define int long long
using namespace std;
int day[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
struct edge {
  int to, cost;
};
typedef pair<int, int> P;

vector<bool> visit(100010, false);
vector<int> d(100010);
vector<edge> g[100010];

void dfs(int v, int parent, int dist) {
  d[v] = dist;
  rep(i, 0, g[v].size()) {
    edge e = g[v][i];
    if (e.to == parent)
      continue;
    dfs(e.to, v, dist + e.cost);
  }
  return;
}

signed main() {
  int n;
  cin >> n;
  rep(i, 0, n - 1) {
    int a, b, c;
    cin >> a >> b >> c;
    a--;
    b--;
    g[a].push_back({b, c});
    g[b].push_back({a, c});
  }
  int q, k;
  cin >> q >> k;
  k--;
  d[k] = 0;
  dfs(k, -1, 0);

  rep(i, 0, q) {
    int x, y;
    cin >> x >> y;
    x--;
    y--;
    cout << d[x] + d[y] << endl;
  }
}
/*
1-21-2
*/