Submission #468560

#	Time	Username	Problem	Language	Result	Execution time	Memory
468560		ACmachine	Mousetrap (CEOI17_mousetrap)	C++17	100 / 100	1695 ms	207928 KiB

mousetrap

#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;
            else
                dp[x] += cum_deg;
        }  
    }
    
    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 (stderr)

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:144:13: note: in expansion of macro 'REP'
  144 |             REP(i, tm.size()){
      |             ^~~

• Subtask 1: 20 / 20
• Subtask 2: 25 / 25
• Subtask 3: 20 / 20
• Subtask 4: 35 / 35