#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, int)> dfs = [&](int v, int p, int d){
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);
cout << dp[m] - 1 << "\n";
/*
int a = m;
int pv = -1;
vector<int> path;
while(a != -1){
path.pb(a);
pv = a;
a = par[a];
}
int cum_deg = 0;
REPD(i, (int)path.size() - 1){
int v = path[i];
int nx = (i == 0 ? -1 : path[i - 1]);
cum_deg += (int)g[v].size() - 1;
for(int x : g[v]){
if(x == nx || x == par[v])
continue;
dp[v] += cum_deg;
}
}
bool check = [&](int maxi){
int num_blocked = 0;
int num_max = 1;
int v = m;
int pv = -1;
vector<int> tm;
while(v != 0){
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_max++;
pv = v;
v = par[v];
}
}
*/
return 0;
}
Compilation message
mousetrap.cpp: In function 'int main()':
mousetrap.cpp:97:14: error: no match for call to '(std::function<void(int, int, int)>) (int&, int)'
97 | dfs(t, -1);
| ^
In file included from /usr/include/c++/10/functional:59,
from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/10/algorithm:74,
from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
from mousetrap.cpp:2:
/usr/include/c++/10/bits/std_function.h:617:5: note: candidate: '_Res std::function<_Res(_ArgTypes ...)>::operator()(_ArgTypes ...) const [with _Res = void; _ArgTypes = {int, int, int}]'
617 | function<_Res(_ArgTypes...)>::
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/10/bits/std_function.h:617:5: note: candidate expects 3 arguments, 2 provided
