#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#include <cstdio>
#include <vector>
#include <utility>
#include <algorithm>
using namespace std;
struct Item {
int posde;
int negde;
int ans;
Item () {}
Item (int posde, int negde, int ans): posde(posde), negde(negde), ans(ans) {}
} sp_split[19][500006];
struct MySet {
int v[3];
MySet() {
v[0] = v[1] = v[2] = 0;
}
void push(int x) {
auto t = min_element(v, v + 3);
if (x > *t) *t = x;
}
void pop(int x) {
*find(v, v + 3, x) = 0;
}
int first() {
return *max_element(v, v + 3);
}
int second() {
return v[0] + v[1] + v[2] - *min_element(v, v + 3);
}
} lt_depth[500006], lt_dist[500006];
int n, m;
vector<int> tree[500006], child[500006];
vector<pair<int, int>> adj[500006];
int depth[500006], sp[19][500006], sp_dist[19][500006];
int max_depth[500006], rev_max_depth[500006], dist[500006], rev_dist[500006];
int prev_dist[500006], prev_depth[500006][2];
inline Item query_sp_res(int A, int x) {
if (A == -1) return Item();
Item ret = { prev_depth[x][0] + depth[x], prev_depth[x][0] - depth[x], (int)-1e9 };
if (A == x) return ret;
for (int t = 18; t >= 0; t--) if (sp[t][x] != -1 && depth[sp[t][x]] > depth[A]) {
ret.ans = max({ sp_split[t][x].ans, ret.ans, sp_split[t][x].posde + ret.negde });
ret.posde = max(sp_split[t][x].posde, ret.posde);
ret.negde = max(sp_split[t][x].negde, ret.negde);
x = sp[t][x];
}
ret.ans = max({ sp_split[0][x].ans, ret.ans, sp_split[0][x].posde + ret.negde });
ret.posde = max(sp_split[0][x].posde, ret.posde);
ret.negde = max(sp_split[0][x].negde, ret.negde);
return ret;
}
int dfs_dist(int x) {
max_depth[x] = 0;
dist[x] = 0;
int mx0 = (int)-1e9, mx1 = (int)-1e9;
for (auto &i: child[x]) {
int t = dfs_dist(i) + 1;
max_depth[x] = max(max_depth[x], t);
if (t > mx0) mx1 = mx0, mx0 = t;
else if (t > mx1) mx1 = t;
dist[x] = max(dist[x], dist[i]);
}
dist[x] = max(dist[x], mx0 + max(mx1, 0));
return max_depth[x];
}
void dfs_rev_dist(int x) {
for (auto &i: child[x]) {
lt_depth[x].push(max_depth[i] + 1);
if (prev_depth[x][0] < max_depth[i] + 1) prev_depth[x][1] = prev_depth[x][0], prev_depth[x][0] = max_depth[i] + 1;
else if (prev_depth[x][1] < max_depth[i] + 1) prev_depth[x][1] = max_depth[i] + 1;
lt_dist[x].push(dist[i]);
if (prev_dist[x] < dist[i]) prev_dist[x] = dist[i];
}
for (auto &i: child[x]) {
lt_depth[x].pop(max_depth[i] + 1);
lt_dist[x].pop(dist[i]);
rev_dist[i] = max({ rev_max_depth[i] = max(lt_depth[x].first(), rev_max_depth[x]) + 1, lt_depth[x].second(), lt_depth[x].first() + rev_dist[x]});
lt_depth[x].push(max_depth[i] + 1);
lt_dist[x].push(dist[i]);
}
for (auto &i: child[x]) dfs_rev_dist(i);
}
void dfs_construct(int x) {
for (auto &i: child[x]) {
lt_dist[x].pop(dist[i]);
sp_dist[0][i] = lt_dist[x].first();
lt_dist[x].push(dist[i]);
lt_depth[x].pop(max_depth[i] + 1);
int V = lt_depth[x].first();
sp_dist[0][i] = max(sp_dist[0][i], lt_depth[x].second());
sp_split[0][i].posde = V + depth[x];
sp_split[0][i].negde = V - depth[x];
lt_depth[x].push(max_depth[i] + 1);
}
for (auto &i: child[x]) dfs_construct(i);
}
void dfs_child(int x, int prev = -1) {
sp[0][x] = prev;
for (auto &i: tree[x]) if (i != prev) {
depth[i] = depth[x] + 1;
child[x].push_back(i);
dfs_child(i, x);
}
}
int A, B;
inline int lca(int u, int v) {
bool sw = false;
if (depth[u] < depth[v]) swap(u, v), sw = true;
int diff = depth[u] - depth[v] - 1;
if (~diff) {
for (int t = 18; t >= 0; t--) if (diff >= 1 << t) {
diff -= 1 << t;
u = sp[t][u];
}
if (sw) B = u;
else A = u;
u = sp[0][u];
if (u == v) return u;
}
for (int t = 18; t >= 0; t--) if (sp[t][u] != -1 && sp[t][v] != -1 && sp[t][u] != sp[t][v]) {
u = sp[t][u];
v = sp[t][v];
}
A = u, B = v;
if (sw) swap(A, B);
return sp[0][u];
}
inline int query_sp_dist(int u, int v, int l, int A, int B) {
int ret = 0;
if (u != l) {
ret = max(prev_depth[u][0] + prev_depth[u][1], prev_dist[u]);
u = sp[0][u];
}
if (v != l) {
ret = max(prev_depth[v][0] + prev_depth[v][1], prev_dist[v]);
v = sp[0][v];
}
for (int t = 18; t >= 0; t--) if (sp[t][u] != -1 && depth[sp[t][u]] > depth[l]) {
ret = max(ret, sp_dist[t][u]);
u = sp[t][u];
}
for (int t = 18; t >= 0; t--) if (sp[t][v] != -1 && depth[sp[t][v]] > depth[l]) {
ret = max(ret, sp_dist[t][v]);
v = sp[t][v];
}
if (A != -1) lt_dist[l].pop(dist[A]);
if (B != -1) lt_dist[l].pop(dist[B]);
ret = max(ret, lt_dist[l].first());
if (A != -1) lt_dist[l].push(dist[A]);
if (B != -1) lt_dist[l].push(dist[B]);
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 });
}
for (int i = 0; i < n; i++) prev_dist[i] = prev_depth[i][0] = prev_depth[i][1] = (int)-1e9;
dfs_child(0);
dfs_dist(0);
dfs_rev_dist(0);
dfs_construct(0);
for (int t = 1; t < 19; t++) for (int i = 0; i < n; i++) {
if (sp[t - 1][i] == -1) {
sp[t][i] = -1;
sp_dist[t][i] = sp_dist[t - 1][i];
sp_split[t][i] = sp_split[t - 1][i];
} else {
sp[t][i] = sp[t - 1][sp[t - 1][i]];
sp_dist[t][i] = max(sp_dist[t - 1][i], sp_dist[t - 1][sp[t - 1][i]]);
sp_split[t][i].ans = max({ sp_split[t - 1][sp[t - 1][i]].ans, sp_split[t - 1][i].ans, sp_split[t - 1][sp[t - 1][i]].posde + sp_split[t - 1][i].negde });
sp_split[t][i].posde = max(sp_split[t - 1][sp[t - 1][i]].posde, sp_split[t - 1][i].posde);
sp_split[t][i].negde = max(sp_split[t - 1][sp[t - 1][i]].negde, sp_split[t - 1][i].negde);
}
}
int res = 2 * (n - 1) - dist[0];
for (int i = 0; i < n; i++) for (auto [ j, w ]: adj[i]) {
A = B = -1;
int l = lca(i, j);
int ds = depth[i] + depth[j] - depth[l] - depth[l];
int curr = w + 2 * (n - 1) - ds - 1;
int G = 0, y = 0;
if (A != -1) lt_depth[l].pop(max_depth[A] + 1);
if (B != -1) lt_depth[l].pop(max_depth[B] + 1);
G = lt_depth[l].first();
y = max({ y, G + rev_max_depth[l] - 1, lt_depth[l].second() - 1 });
if (A != -1) lt_depth[l].push(max_depth[A] + 1);
if (B != -1) lt_depth[l].push(max_depth[B] + 1);
Item first = query_sp_res(A, i);
Item second = query_sp_res(B, j);
int Alt = first.negde + depth[l];
int Brt = second.negde + depth[l];
int Lt = max(rev_max_depth[l], G);
res = min(res, curr - max({ y, Alt + max(Brt, Lt) + 1, max(Alt, Lt) + Brt + 1, first.ans + 1, second.ans + 1, rev_dist[l] - 1, query_sp_dist(i, j, l, A, B) - 1 }));
}
printf("%d", res);
}
Compilation message
Main.cpp: In function 'int main()':
Main.cpp:171:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
171 | scanf("%d%d", &n, &m);
| ~~~~~^~~~~~~~~~~~~~~~
Main.cpp:174:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
174 | scanf("%d%d%d", &x, &y, &w);
| ~~~~~^~~~~~~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
25 ms |
47684 KB |
Output is correct |
| 2 |
Correct |
26 ms |
47720 KB |
Output is correct |
| 3 |
Incorrect |
27 ms |
47744 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
25 ms |
47684 KB |
Output is correct |
| 2 |
Correct |
26 ms |
47720 KB |
Output is correct |
| 3 |
Incorrect |
27 ms |
47744 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
35 ms |
50680 KB |
Output is correct |
| 2 |
Correct |
34 ms |
50848 KB |
Output is correct |
| 3 |
Correct |
37 ms |
50632 KB |
Output is correct |
| 4 |
Correct |
36 ms |
50476 KB |
Output is correct |
| 5 |
Correct |
34 ms |
50320 KB |
Output is correct |
| 6 |
Correct |
31 ms |
49996 KB |
Output is correct |
| 7 |
Correct |
33 ms |
50764 KB |
Output is correct |
| 8 |
Correct |
35 ms |
50484 KB |
Output is correct |
| 9 |
Correct |
33 ms |
50764 KB |
Output is correct |
| 10 |
Correct |
35 ms |
50376 KB |
Output is correct |
| 11 |
Incorrect |
34 ms |
50620 KB |
Output isn't correct |
| 12 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
25 ms |
47684 KB |
Output is correct |
| 2 |
Correct |
26 ms |
47720 KB |
Output is correct |
| 3 |
Incorrect |
27 ms |
47744 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
25 ms |
47684 KB |
Output is correct |
| 2 |
Correct |
26 ms |
47720 KB |
Output is correct |
| 3 |
Incorrect |
27 ms |
47744 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
25 ms |
47684 KB |
Output is correct |
| 2 |
Correct |
26 ms |
47720 KB |
Output is correct |
| 3 |
Incorrect |
27 ms |
47744 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
25 ms |
47684 KB |
Output is correct |
| 2 |
Correct |
26 ms |
47720 KB |
Output is correct |
| 3 |
Incorrect |
27 ms |
47744 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
25 ms |
47684 KB |
Output is correct |
| 2 |
Correct |
26 ms |
47720 KB |
Output is correct |
| 3 |
Incorrect |
27 ms |
47744 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
