#include <bits/stdc++.h>
using namespace std;
int n;
vector<int> G[200005];
int p[200005];
int col[200005];
int sz[200005];
int root;
void dfs(int u){
sz[u] = 1;
for (auto v : G[u]){
if (v == p[u]) continue;
p[v] = u;
dfs(v);
sz[u] += sz[v];
}
}
int findcentroid(int u){
for (auto v : G[u]){
if (v == p[u]) continue;
if (sz[v] > n/2) return findcentroid(v);
}
return u;
}
vector<int> COL[200005];
set<int> rest;
set<int> hmm;
int curcol = 1;
void dfs2(int u){
sz[u] = 1;
COL[col[u]].push_back(u);
for (auto v : G[u]){
if (p[u] == v) continue;
//printf("%d -> %d\n",u,v);
p[v] = u;
if (u == root){
col[v] = curcol++;
}
else col[v] = col[u];
dfs2(v);
sz[u] += sz[v];
}
}
int ans;
void process(int a, int b, int c){
ans = min(ans, max(a,max(b,c)) - min(a,min(b,c)));
}
int main(){
scanf("%d",&n);
ans = n;
for (int i = 0; i < n-1; i++){
int x,y;
scanf("%d%d",&x,&y);
G[x].push_back(y);
G[y].push_back(x);
}
p[1] = -1;
dfs(1);
root = findcentroid(1);
for (int i = 1; i <= n; i++) p[i] = -1;
col[root] = 0;
dfs2(root);
//printf("centroid is %d\n",root);
for (int c = 1; c <= curcol; c++){
for (auto u : COL[c]){
//printf("col %d: %d\n",c,u);
}
for (auto u : COL[c]){
hmm.insert(sz[u]);
}
for (auto u : COL[c]){
int a = sz[u];
int bad = n-a;
///search inside
auto it = hmm.lower_bound(a+bad/2);
if (it != hmm.end()){
int b = *it - a;
int c = n-a-b;
process(a,b,c);
}
it = hmm.upper_bound(a+bad/2);
if (it != hmm.end()){
int b = *it - a;
int c = n-a-b;
process(a,b,c);
}
/// search outside
it = rest.lower_bound(bad/2);
if (it != rest.end()){
int b = *it;
int c = n-a-b;
process(a,b,c);
}
it = rest.upper_bound(bad/2);
if (it != hmm.end()){
int b = *it;
int c = n-a-b;
process(a,b,c);
}
//printf("after checking %d, ans = %d\n",u,ans);
}
for (auto u : COL[c]){
rest.insert(sz[u]);
}
hmm.clear();
}
printf("%d",ans);
}
Compilation message
papricice.cpp: In function 'int main()':
papricice.cpp:65:19: warning: unused variable 'u' [-Wunused-variable]
65 | for (auto u : COL[c]){
| ^
papricice.cpp:49:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
49 | scanf("%d",&n);
| ~~~~~^~~~~~~~~
papricice.cpp:53:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
53 | scanf("%d%d",&x,&y);
| ~~~~~^~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
7 ms |
9836 KB |
Output is correct |
| 2 |
Correct |
7 ms |
9708 KB |
Output is correct |
| 3 |
Incorrect |
7 ms |
9708 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
7 ms |
9836 KB |
Output is correct |
| 2 |
Correct |
7 ms |
9708 KB |
Output is correct |
| 3 |
Incorrect |
7 ms |
9708 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
7 ms |
9836 KB |
Output is correct |
| 2 |
Correct |
7 ms |
9708 KB |
Output is correct |
| 3 |
Incorrect |
7 ms |
9708 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
