#include <bits/stdc++.h>
using namespace std;
using LL = long long;
#define watch(x) cerr << (#x) << " is " << x << endl
vector<bool> vis, cycle;
vector<array<LL, 2>> prv, nxt;
vector<LL> dl, dr;
vector<LL> f;
LL max_path(const vector<int>& c, const vector<vector<array<LL, 3>>>& adj) {
auto find_cycle = [&](auto&& self, int v, int pid = -1) -> bool {
if (vis[v]) return cycle[v] = true;
vis[v] = true;
for (auto [u, w, eid] : adj[v]) {
if (eid == pid) continue;
bool works = self(self, u, v);
if (works) {
nxt[v] = {u, w};
prv[u] = {v, w};
return cycle[v] ? false : cycle[v] = true;
}
}
return false;
};
find_cycle(find_cycle, c[0]);
LL dep = 0;
auto path_in_tree = [&](auto&& self, int v, int p = -1) -> LL {
while (dep++ > 10000 || v == -1) ;
LL ans = 0;
for (auto [u, w, eid] : adj[v]) {
if (u == p || u == prv[v][0] || u == nxt[v][0]) continue;
ans = max(ans, w + self(self, u, v));
}
return ans;
};
int start = -1;
for (int i : c) {
if (cycle[i]) {
start = i;
f[i] = path_in_tree(path_in_tree, i);
}
}
return 42;
// multiset<LL> L, R;
// {
// int v = start;
// int u = start;
// dl[v] = dr[u] = 0;
// do {
// auto [nv, lw] = nxt[v];
// auto [nu, rw] = prv[u];
// if (v != start) L.insert(f[v] + dl[v]);
// if (u != start) R.insert(f[u] + dr[u]);
// if (nv != start) dl[nv] = dl[v] + lw;
// dr[nu] = dr[u] + rw;
// v = nv;
// u = nu;
// } while (v != start);
// }
// assert(dl[start] == 0);
// LL len = dr[start];
// LL bias = 0;
// LL ans = 0;
// {
// int v = start;
// do {
// // watch(v);
// // watch(bias);
// // cerr << "L: "; for (LL i : L) cerr << i << " "; cerr << endl;
// // cerr << "R: "; for (LL i : R) cerr << i << " "; cerr << endl;
// // cerr << endl;
// ans = max(ans, *prev(L.end()) - bias + f[v]);
// ans = max(ans, *prev(R.end()) + bias + f[v]);
// int nv = nxt[v][0];
// if (nv == start) break;
// bias += nxt[v][1];
// L.insert(f[v] + dl[v] + len);
// R.insert(f[v] + dr[v] - len);
// if (L.count(f[nv] + dl[nv])) L.erase(L.find(f[nv] + dl[nv]));
// if (R.count(f[nv] + dr[nv])) R.erase(R.find(f[nv] + dr[nv]));
// v = nv;
// } while (v != start);
// }
// return ans;
}
int main() {
#ifdef LORENZO
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
int n; cin >> n;
vector<vector<array<LL, 3>>> adj(n);
for (int i = 0; i < n; ++i) {
int a; cin >> a; --a;
int w; cin >> w;
adj[i].push_back({a, w, i});
adj[a].push_back({i, w, i});
}
vis.assign(n, false);
vector<vector<int>> cc;
auto dfs = [&](auto&& self, int v) -> void {
vis[v] = true;
cc.back().push_back(v);
for (auto [u, _, __] : adj[v]) {
if (!vis[u]) {
self(self, u);
}
}
};
for (int i = 0; i < n; ++i) {
if (!vis[i]) {
cc.push_back(vector<int>(0));
dfs(dfs, i);
}
}
f.assign(n, 0);
dl.assign(n, 1e18);
dr.assign(n, 1e18);
prv.assign(n, {-1,-1});
nxt.assign(n, {-1,-1});
vis.assign(n, false);
cycle.assign(n, false);
LL ans = 0;
for (const auto& c : cc) {
ans += max_path(c, adj);
}
cout << ans << "\n";
}
Compilation message
islands.cpp: In function 'LL max_path(const std::vector<int>&, const std::vector<std::vector<std::array<long long int, 3> > >&)':
islands.cpp:38:7: warning: variable 'start' set but not used [-Wunused-but-set-variable]
38 | int start = -1;
| ^~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 2 |
Execution timed out |
2058 ms |
340 KB |
Time limit exceeded |
| 3 |
Incorrect |
1 ms |
340 KB |
Output isn't correct |
| 4 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 5 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 6 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 7 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 8 |
Execution timed out |
2078 ms |
724 KB |
Time limit exceeded |
| 9 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 10 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 11 |
Incorrect |
1 ms |
212 KB |
Output isn't correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
2084 ms |
760 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
2081 ms |
1108 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
2063 ms |
2900 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
2066 ms |
8348 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
2088 ms |
31460 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
2078 ms |
60796 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
819 ms |
131072 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
885 ms |
131072 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
