#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T, typename U> using ordered_map = tree<T, U, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
#define FOR(i,j,k,in) for(int i=(j); i < (k);i+=in)
#define FORD(i,j,k,in) for(int i=(j); i >=(k);i-=in)
#define REP(i,b) FOR(i,0,b,1)
#define REPD(i,b) FORD(i,b,0,1)
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define all(x) begin(x), end(x)
#define MANY_TESTS int tcase; cin >> tcase; while(tcase--)
const double EPS = 1e-9;
const int MOD = 1e9+7;
const ll INFF = 1e18;
const int INF = 1e9;
const ld PI = acos((ld)-1);
const vi dy = {1, 0, -1, 0, -1, 1, 1, -1};
const vi dx = {0, 1, 0, -1, -1, 1, -1, 1};
void DBG(){cout << "]" << endl;}
template<typename T, typename ...U> void DBG(const T& head, const U... args){ cout << head << "; "; DBG(args...); }
#define dbg(...) cout << "Line(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__);
#define chk() cout << "Check at line(" << __LINE__ << ") hit." << endl;
template<class T, unsigned int U>
ostream& operator<<(ostream& out, const array<T, U> &v){out << "["; REP(i, U) out << v[i] << ", "; out << "]"; return out;}
template <class T, class U>
ostream& operator<<(ostream& out, const pair<T, U> &par) {out << "[" << par.first << ";" << par.second << "]"; return out;}
template <class T>
ostream& operator<<(ostream& out, const set<T> &cont) { out << "{"; for( const auto &x:cont) out << x << ", "; out << "}"; return out; }
template <class T, class U>
ostream& operator<<(ostream& out, const map<T, U> &cont) {out << "{"; for( const auto &x:cont) out << x << ", "; out << "}"; return out; }
template<class T>
ostream& operator<<(ostream& out, const vector<T> &v){ out << "["; REP(i, v.size()) out << v[i] << ", "; out << "]"; return out;}
template<class T>
istream& operator>>(istream& in, vector<T> &v){ for(auto &x : v) in >> x; return in; }
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int n, t, m;
cin >> n >> t >> m;
t--; m--;
vector<vector<int>> g(n);
REP(i, n - 1){
int a, b;
cin >> a >> b;
a--; b--;
g[a].pb(b);
g[b].pb(a);
}
vector<int> dp(n, INF);
vector<int> par(n, -1);
function<void(int, int)> tmd = [&](int v, int p){
par[v] = p;
for(int x : g[v]){
if(x == p) continue;
tmd(x, v);
}
};
tmd(t, -1);
vector<int> path;
vector<bool> onpath(n, false);
int vv = m;
while(vv != -1){
path.pb(vv);
onpath[vv] = true;
vv = par[vv];
}
function<void(int, int, int)> dfs = [&](int v, int p, int d){
if(onpath[v])
d = 0;
par[v] = p;
vector<int> vect;
for(int x : g[v]){
if(x == p) continue;
dfs(x, v, d + 1);
}
sort(all(g[v]), [&](int lhs, int rhs){
return dp[lhs] > dp[rhs];
});
for(int x : g[v]){
if(x == p)
continue;
vect.pb(dp[x]);
}
if(vect.size() == 0)
dp[v] = d;
else if(vect.size() == 1)
dp[v] = 1 + d;
else{
dp[v] = (int)vect.size() - 1 + vect[1];
}
};
dfs(t, -1, 0);
int cum_deg = 0;
REPD(i, (int)path.size() - 2){
int v = path[i];
int nx = (i == 0 ? -1 : path[i - 1]);
cum_deg += (int)g[v].size() - 2;
for(int x : g[v]){
if(x == nx || x == par[v])
continue;
if(i != 0)
dp[x] += cum_deg - 1;
}
}
//dbg(dp)
auto check = [&](int maxi){
int num_blocked = 0;
int num_max = min(maxi, 1);
int v = m;
int pv = -1;
vector<int> tm;
int num_blocked_layer = 0;
while(v != t){
tm = vector<int>();
for(int x : g[v]){
if(x == par[v] || x == pv)
continue;
tm.pb(dp[x]);
}
REP(i, tm.size()){
if(tm[i] + num_blocked_layer > maxi){
if(num_blocked == num_max)
return false;
num_blocked++;
}
}
//dbg(v, tm, maxi);
num_max = min(num_max + 1, maxi);
pv = v;
v = par[v];
num_blocked_layer = num_blocked;
}
return true;
};
int ans = 0;
REP(i, 3 * n){
if(check(i)){
ans = i;
break;
}
}
cout << ans << "\n";
return 0;
}
Compilation message
mousetrap.cpp: In lambda function:
mousetrap.cpp:19:40: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
19 | #define FOR(i,j,k,in) for(int i=(j); i < (k);i+=in)
| ^
mousetrap.cpp:21:18: note: in expansion of macro 'FOR'
21 | #define REP(i,b) FOR(i,0,b,1)
| ^~~
mousetrap.cpp:142:13: note: in expansion of macro 'REP'
142 | REP(i, tm.size()){
| ^~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
204 KB |
Output is correct |
| 2 |
Correct |
0 ms |
204 KB |
Output is correct |
| 3 |
Correct |
0 ms |
204 KB |
Output is correct |
| 4 |
Correct |
0 ms |
204 KB |
Output is correct |
| 5 |
Correct |
1 ms |
204 KB |
Output is correct |
| 6 |
Correct |
1 ms |
204 KB |
Output is correct |
| 7 |
Incorrect |
0 ms |
204 KB |
Output isn't correct |
| 8 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
415 ms |
63160 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
204 KB |
Output is correct |
| 2 |
Correct |
0 ms |
204 KB |
Output is correct |
| 3 |
Correct |
0 ms |
204 KB |
Output is correct |
| 4 |
Correct |
0 ms |
204 KB |
Output is correct |
| 5 |
Correct |
1 ms |
204 KB |
Output is correct |
| 6 |
Correct |
1 ms |
204 KB |
Output is correct |
| 7 |
Incorrect |
0 ms |
204 KB |
Output isn't correct |
| 8 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
204 KB |
Output is correct |
| 2 |
Correct |
0 ms |
204 KB |
Output is correct |
| 3 |
Correct |
0 ms |
204 KB |
Output is correct |
| 4 |
Correct |
0 ms |
204 KB |
Output is correct |
| 5 |
Correct |
1 ms |
204 KB |
Output is correct |
| 6 |
Correct |
1 ms |
204 KB |
Output is correct |
| 7 |
Incorrect |
0 ms |
204 KB |
Output isn't correct |
| 8 |
Halted |
0 ms |
0 KB |
- |
