#include <bits/stdc++.h> using namespace std; typedef int ll; const int mn = (1 << 20) + 5; ll n, a[mn], st, en, t, p[mn][21], d[mn][21], dp[mn][42], in[mn], out[mn], ti, f[100][100], o[100][100], dst[100][100], dep[mn]; vector<pair<ll, ll> > v[mn]; vector<ll> g, sk; void dfs(ll i, ll pa, ll s){ in[i] = ++ti; p[i][0] = pa; d[i][0] = s; dep[i] = dep[pa] + 1; // cout << i << " " << d[i][0] << " "; for(int j = 1; j <= 20; ++j) p[i][j] = p[p[i][j - 1]][j - 1]; for(int j = 1; j <= 20; ++j) d[i][j] = (d[p[i][j - 1]][j - 1] | d[i][j - 1]); // , cout << d[i][j] << " "; // cout << "\n"; for(auto j : v[i]){ if(j.first == pa) continue; if(j.second == -1) dfs(j.first, i, 0); else dfs(j.first, i, (1 << j.second)); } out[i] = ti; } bool anc(ll a, ll b){ return in[a] <= in[b] && out[b] <= out[a]; } ll lca(ll a, ll b){ if(anc(a, b)) return a; if(anc(b, a)) return b; for(int j = 20; j >= 0; --j){ if(!anc(p[a][j], b)) a = p[a][j]; } return p[a][0]; } ll cal(ll a, ll b, ll u){ ll ans = 0; for(int j = 20; j >= 0; --j){ if(!anc(p[a][j], u)) ans |= d[a][j], a = p[a][j]; } if(a != u) ans |= d[a][0]; for(int j = 20; j >= 0; --j){ if(!anc(p[b][j], u)) ans |= d[b][j], b = p[b][j]; } if(b != u) ans |= d[b][0]; return ans; } void solve(){ cin >> n >> st >> en; sk.push_back(st); for(int i = 1; i < n; ++i){ ll x, y, w; cin >> x >> y >> w; if(w > 0) sk.push_back(x), sk.push_back(y), sk.push_back(w); if(w > 0) g.push_back(w), w = (int)g.size() - 1; else w = -1; v[x].push_back({y, w}); v[y].push_back({x, w}); } sk.push_back(en); ti = 0; t = g.size(); dfs(1, 1, 0); memset(dp, -1, sizeof(dp)); dp[0][0] = 0; ll ans = 1e9; // for(auto i : sk) cout << i << " "; // cout << "\n"; for(int i = 0; i < 3 * t + 2; ++i) for(int j = 0; j < 3 * t + 2; ++j){ f[i][j] = lca(sk[i], sk[j]); o[i][j] = cal(sk[i], sk[j], f[i][j]); dst[i][j] = dep[sk[i]] + dep[sk[j]] - 2 * dep[f[i][j]]; // cout << i << " " << j << " " << f[i][j] << " " << o[i][j] << "\n"; } for(int i = 0; i < (1 << t); ++i) for(int j = 0; j <= 2 * t; ++j){ if(dp[i][j] == -1) continue; // cout << i << " " << j << " " << dp[i][j] << " "; ll s; if(j == 0) s = 0; else if(j % 2) s = 3 * ((j - 1) / 2) + 1; else s = 3 * ((j - 1) / 2) + 2; // cout << s << " " << sk[s] << "\n"; for(int k = 0; k < t; ++k){ if((i >> k) & 1) continue; ll r = (o[s][3 * k + 3] | o[3 * k + 3][3 * k + 1]); // cout << k << "* "; // cout << r << " "; if((i & r) == r){ ll nw = dp[i][j] + dst[s][3 * k + 3] + dst[3 * k + 3][3 * k + 1], mask = (i ^ (1 << k)); if(dp[mask][2 * k + 1] == -1) dp[mask][2 * k + 1] = nw; else dp[mask][2 * k + 1] = min(dp[mask][2 * k + 1], nw); } r = (o[s][3 * k + 3] | o[3 * k + 3][3 * k + 2]); // cout << r << "\n"; if((i & r) == r){ ll nw = dp[i][j] + dst[s][3 * k + 3] + dst[3 * k + 3][3 * k + 2], mask = (i ^ (1 << k)); if(dp[mask][2 * k + 2] == -1) dp[mask][2 * k + 2] = nw; else dp[mask][2 * k + 2] = min(dp[mask][2 * k + 2], nw); } } ll r = o[s][3 * t + 1]; if((i & r) == r){ // cout << i << " " << j << "- \n"; ans = min(ans, dp[i][j] + dst[s][3 * t + 1]); } } if(ans == 1e9) cout << -1; else cout << ans; return; } int main(){ ios_base::sync_with_stdio(false); cin.tie(NULL); if(fopen(".INP", "r")) { freopen(".INP", "r", stdin); freopen(".OUT", "w", stdout); } int testCase = 1; //cin >> testCase; while(testCase--) solve(); }

Main.cpp: In function 'int main()':
Main.cpp:122:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  122 |                 freopen(".INP", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~
Main.cpp:123:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  123 |                 freopen(".OUT", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~