#include <set>
#include <cstdio>
#include <vector>
#include <utility>
#include <algorithm>
using namespace std;
int n, m;
vector<int> tree[200006], child[200006];
vector<pair<int, int>> adj[200006];
int _par[200006], _sz[200006];
int sz[200006], depth[200006], par[200006];
int in[200006], top[100006], T;
int dfs(int x, int prev = -1) {
_par[x] = prev;
_sz[x] = 1;
for (auto &i: tree[x]) if (i != prev) {
_sz[x] = max(_sz[x], dfs(i, x) + 1);
}
return _sz[x];
}
int max_depth[200006], rev_max_depth[200006], dist[200006], rev_dist[200006];
int dfs_dist(int x) {
vector<int> v;
max_depth[x] = 0;
dist[x] = 0;
for (auto &i: child[x]) {
v.push_back(dfs_dist(i) + 1);
max_depth[x] = max(max_depth[x], v.back());
dist[x] = max(dist[x], dist[i]);
}
int v0 = max_element(v.begin(), v.end()) - v.begin();
int X = v[v0];
if (!v.empty()) v[v0] = 0;
int v1 = max_element(v.begin(), v.end()) - v.begin();
v[v0] = X;
if (!v.empty()) dist[x] = max(dist[x], v[v0]);
if ((int)v.size() > 1) dist[x] = max(dist[x], v[v0] + v[v1]);
return max_depth[x];
}
void dfs_rev_dist(int x) {
multiset<int> v, u, w;
if (par[x] != -1) {
v.insert(rev_max_depth[x]);
u.insert(rev_dist[x]);
}
for (auto &i: child[x]) {
v.insert(max_depth[i] + 1);
u.insert(dist[i]);
}
for (auto &i: child[x]) {
v.erase(v.find(max_depth[i] + 1));
u.erase(u.find(dist[i]));
if (!u.empty()) rev_dist[i] = *u.rbegin();
if (!v.empty()) rev_dist[i] = max(rev_dist[i], rev_max_depth[i] = *v.rbegin() + 1);
if ((int)v.size() > 1) rev_dist[i] = max(rev_dist[i], *v.rbegin() + *prev(prev(v.end())));
v.insert(max_depth[i] + 1);
u.insert(dist[i]);
}
for (auto &i: child[x]) dfs_rev_dist(i);
}
void dfs_child(int x, int prev = -1) {
par[x] = prev;
for (auto &i: tree[x]) if (i != prev) {
child[x].push_back(i);
dfs_child(i, x);
}
}
int dfs_sz(int x) {
sz[x] = 1;
for (auto &i: child[x]) {
depth[i] = depth[x] + 1;
sz[x] += dfs_sz(i);
if (sz[i] > sz[child[x][0]]) swap(child[x][0], i);
}
return sz[x];
}
void dfs_hld(int x) {
in[x] = T++;
for (auto &i: child[x]) {
top[i] = (i == child[x][0] ? top[x] : i);
dfs_hld(i);
}
}
int lca(int u, int v) {
int ret = 0;
while (top[u] != top[v]) {
if (depth[top[u]] < depth[top[v]]) swap(u, v);
ret += depth[u] - depth[par[top[u]]];
u = par[top[u]];
}
if (depth[u] > depth[v]) swap(u, v);
return u;
}
int tree_dist[524288];
int query_dist(int i, int b, int e, int l, int r) {
if (r < l || r < b || e < l) return 0;
if (l <= b && e <= r) return tree_dist[i];
int m = (b + e) / 2;
return max(query_dist(i * 2 + 1, b, m, l, r), query_dist(i * 2 + 2, m + 1, e, l, r));
}
vector<pair<int, int>> lt;
void query_hld(int u, int v) {
while (top[u] != top[v]) {
if (depth[top[u]] < depth[top[v]]) swap(u, v);
lt.push_back({ in[top[u]], in[u] });
u = par[top[u]];
}
lt.push_back({ min(in[u], in[v]), max(in[u], in[v]) });
}
int query_hld_dist(int u, int v) {
lt.clear();
query_hld(u, v);
sort(lt.begin(), lt.end());
int ret = max(query_dist(0, 0, 262143, 0, lt[0].first - 1), query_dist(0, 0, 262143, lt.back().second + 1, 262143));
for (int i = 1; i < (int)lt.size(); i++) ret = max(ret, query_dist(0, 0, 262143, lt[i - 1].second + 1, lt[i].first - 1));
return ret;
}
int main() {
scanf("%d%d", &n, &m);
while (m--) {
int x, y, w;
scanf("%d%d%d", &x, &y, &w);
if (w == 1) {
tree[x].push_back(y);
tree[y].push_back(x);
} else {
adj[x].push_back({ y, w });
adj[y].push_back({ x, w });
}
}
dfs_child(0);
dfs_sz(0);
dfs_hld(0);
dfs_dist(0);
dfs_rev_dist(0);
for (int i = 0; i < n; i++) tree_dist[262143 + in[i]] = dist[i];
for (int i = 262142; i >= 0; i--) tree_dist[i] = max(tree_dist[i * 2 + 1], tree_dist[i * 2 + 2]);
int zero = 2 * (n - 1) - dist[0], one = (int)1e9;
for (int i = 0; i < n; i++) {
dfs(i);
for (auto &j: adj[i]) if (i < j.first) {
int l = lca(i, j.first);
int ds = depth[i] + depth[j.first] - depth[l] - depth[l];
int curr = j.second + 2 * (n - 1) - ds - 1;
int x = j.first, pv = -1;
vector<pair<int, int>> v;
int y = max(rev_dist[l] - 1, query_hld_dist(i, j.first)), T = 0;
while (x != -1) {
for (auto &k: tree[x]) if (k != pv && k != _par[x]) {
if (_sz[k]) {
if (!v.empty() && v.back().second == T) {
y = max(y, v.back().first + _sz[k] - 1);
v.back().first = max(v.back().first, _sz[k]);
} else v.push_back({ _sz[k], T });
}
}
T++;
pv = x;
x = _par[x];
}
int ans = -(int)1e9;
for (int i = 0; i < (int)v.size(); i++) {
if (i) ans -= v[i].second - v[i - 1].second;
y = max(y, ans + v[i].first + 1);
ans = max(ans, v[i].first);
}
curr -= y;
one = min(one, curr);
}
}
printf("%d", min(zero, one));
}
Compilation message
Main.cpp: In function 'int main()':
Main.cpp:134:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
134 | scanf("%d%d", &n, &m);
| ~~~~~^~~~~~~~~~~~~~~~
Main.cpp:137:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
137 | scanf("%d%d%d", &x, &y, &w);
| ~~~~~^~~~~~~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
8 ms |
15436 KB |
Output is correct |
| 2 |
Incorrect |
9 ms |
15460 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
8 ms |
15436 KB |
Output is correct |
| 2 |
Incorrect |
9 ms |
15460 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
869 ms |
17864 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
8 ms |
15436 KB |
Output is correct |
| 2 |
Incorrect |
9 ms |
15460 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
8 ms |
15436 KB |
Output is correct |
| 2 |
Incorrect |
9 ms |
15460 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
8 ms |
15436 KB |
Output is correct |
| 2 |
Incorrect |
9 ms |
15460 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
8 ms |
15436 KB |
Output is correct |
| 2 |
Incorrect |
9 ms |
15460 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
8 ms |
15436 KB |
Output is correct |
| 2 |
Incorrect |
9 ms |
15460 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
