#include <iostream>
#include <vector>
#include <algorithm>
typedef long long ll;
using namespace std;
const int maxn = 1e6 + 5;
vector<bool> vis(maxn, false);
vector<pair<int, ll> > p(maxn, { -1, 0 });
vector<vector<pair<int, int> > > g(maxn);
void dfs1(int u, int& a, int& b, ll &l, vector<int>& v)
{
v.push_back(u); vis[u] = true;
for (const pair<int, int>& i : g[u])
{
if (!vis[i.first]) p[i.first] = { u, i.second }, dfs1(i.first, a, b, l, v);
else if (i.first != p[u].first) a = i.first, b = u, l = i.second;
}
}
pair<ll, int> dfs2(int u, int p, ll d)
{
pair<ll, int> ans(d, u);
for (const pair<int, int>& i : g[u]) if (!vis[i.first] && i.first != p)
ans = max(ans, dfs2(i.first, u, d + i.second));
return ans;
}
void del(int u, int v, int l)
{
for (int i = 0; i < g[u].size(); i++) if (g[u][i] == make_pair(v, l))
{
g[u].erase(g[u].begin() + i);
break;
}
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
int n; cin >> n;
for (int i = 0, u, l; i < n; i++) cin >> u >> l, g[--u].push_back({ i, l }), g[i].push_back({ u, l });
ll ans = 0;
for (int i = 0; i < n; i++) if (!vis[i])
{
int u, v; ll l; vector<int> c;
dfs1(i, u, v, l, c); // u je ten nizsi, v je ten vyssi
del(u, v, l), del(v, u, l);
for (int j : c) vis[j] = false;
int v1 = dfs2(i, -1, 0).second;
ll maxi = dfs2(v1, -1, 0).first;
vector<int> path;
for (int j = u; j != p[v].first; j = p[j].first)
path.push_back(j), vis[j] = true;
int k = path.size();
vector<ll> best, pf(k, 0), sf(k, 0);
for (int j : path)best.push_back(dfs2(j, -1, 0).first);
ll len = 0;
for (int j = 0; j < path.size(); j++)
{
if (j) len += p[path[j-1]].second;
pf[j] = len + best[j];
if (j) pf[j] = max(pf[j], pf[j - 1]);
} len = 0;
for (int j = path.size() - 1; j >= 0; j--)
{
if (j != path.size()-1) len += p[path[j]].second;
sf[j] = len + best[j];
if (j != path.size() - 1) sf[j] = max(sf[j], sf[j + 1]);
}
for (int j = 0; j+1 < path.size(); j++)
maxi = max(maxi, l + pf[j] + sf[j + 1]);
ans += maxi;
for (int j : c) vis[j] = true;
}
cout << ans << "\n";
return 0;
}
Compilation message
islands.cpp: In function 'void del(int, int, int)':
islands.cpp:29:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
29 | for (int i = 0; i < g[u].size(); i++) if (g[u][i] == make_pair(v, l))
| ~~^~~~~~~~~~~~~
islands.cpp: In function 'int main()':
islands.cpp:57:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
57 | for (int j = 0; j < path.size(); j++)
| ~~^~~~~~~~~~~~~
islands.cpp:65:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
65 | if (j != path.size()-1) len += p[path[j]].second;
| ~~^~~~~~~~~~~~~~~~
islands.cpp:67:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
67 | if (j != path.size() - 1) sf[j] = max(sf[j], sf[j + 1]);
| ~~^~~~~~~~~~~~~~~~~~
islands.cpp:69:29: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
69 | for (int j = 0; j+1 < path.size(); j++)
| ~~~~^~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
21 ms |
39500 KB |
Output is correct |
| 2 |
Correct |
21 ms |
39496 KB |
Output is correct |
| 3 |
Correct |
22 ms |
39628 KB |
Output is correct |
| 4 |
Correct |
20 ms |
39592 KB |
Output is correct |
| 5 |
Correct |
21 ms |
39500 KB |
Output is correct |
| 6 |
Correct |
21 ms |
39496 KB |
Output is correct |
| 7 |
Correct |
21 ms |
39556 KB |
Output is correct |
| 8 |
Correct |
20 ms |
39500 KB |
Output is correct |
| 9 |
Correct |
21 ms |
39548 KB |
Output is correct |
| 10 |
Correct |
21 ms |
39528 KB |
Output is correct |
| 11 |
Correct |
21 ms |
39552 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
21 ms |
39628 KB |
Output is correct |
| 2 |
Correct |
24 ms |
39628 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
23 ms |
39628 KB |
Output is correct |
| 2 |
Correct |
25 ms |
40084 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
29 ms |
40636 KB |
Output is correct |
| 2 |
Correct |
42 ms |
43436 KB |
Output is correct |
| 3 |
Correct |
34 ms |
40828 KB |
Output is correct |
| 4 |
Correct |
27 ms |
40180 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
61 ms |
44920 KB |
Output is correct |
| 2 |
Correct |
64 ms |
46876 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
130 ms |
52912 KB |
Output is correct |
| 2 |
Correct |
139 ms |
59788 KB |
Output is correct |
| 3 |
Correct |
162 ms |
72836 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
187 ms |
61132 KB |
Output is correct |
| 2 |
Correct |
265 ms |
92348 KB |
Output is correct |
| 3 |
Correct |
304 ms |
98708 KB |
Output is correct |
| 4 |
Correct |
348 ms |
126644 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
403 ms |
102212 KB |
Output is correct |
| 2 |
Runtime error |
888 ms |
131076 KB |
Execution killed with signal 9 |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
444 ms |
131076 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
