Submission #1123009

#	Time	Username	Problem	Language	Result	Execution time	Memory
1123009		Requiem	Hard route (IZhO17_road)	C++20	52 / 100	503 ms	8096 KiB

road

#include<bits/stdc++.h>
#define int long long
#define pb push_back
#define fast ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#define MOD 1000000007
#define inf 1e18
#define fi first
#define se second
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define FORD(i,a,b) for(int i=a;i>=b;i--)
#define sz(a) ((int)(a).size())
#define endl '\n'
#define pi 3.14159265359
#define TASKNAME "hardroute"
using namespace std;
template<typename T> bool maximize(T &res, const T &val) { if (res < val){ res = val; return true; }; return false; }
template<typename T> bool minimize(T &res, const T &val) { if (res > val){ res = val; return true; }; return false; }
typedef pair<int,int> ii;
typedef pair<int,ii> iii;
typedef vector<int> vi;
const int MAXN = 3e5 + 9;
int n;
ii edge[MAXN];
vector<int> g[MAXN];

namespace subtask2{
    bool check(){
        return true;
    }

    int dp[MAXN], deg[MAXN], mx[MAXN], ans = 0, cnt_ans = 0;

    void dfs1(int u, int p){
        dp[u] = 0;
        mx[u] = 0;
        for(auto id: g[u]){
            int v = edge[id].se + edge[id].fi - u;
            if (v == p) continue;
            dfs1(v, u);

            maximize(dp[u], dp[v] + 1);
        }
    }

    void dfs2(int u, int p, int d, int d_out){

        if (deg[u] == 1 and d != 0) {
            if (maximize(ans, d * d_out)) cnt_ans = 1;
            else if (ans == d * d_out) cnt_ans++;
        }

        int mxd = 0;
        for(auto id: g[u]){
            int v = edge[id].se + edge[id].fi - u;
            if (v == p) continue;
            maximize(mx[v], mxd);
            maximize(mxd, dp[v] + 1);
        }
        reverse(g[u].begin(), g[u].end());

        mxd = 0;
        for(auto id: g[u]){
            int v = edge[id].se + edge[id].fi - u;
            if (v == p) continue;
            maximize(mx[v], mxd);
            maximize(mxd, dp[v] + 1);
        }

        for(auto id: g[u]){
            int v = edge[id].se + edge[id].fi - u;
            if (v == p) continue;
            dfs2(v, u, d + 1, max(d_out, mx[v]));
        }
    }

    void solve(){
        FOR(i, 1, n - 1){
            deg[edge[i].fi]++;
            deg[edge[i].se]++;
        }
        FOR(i, 1, n){
            if (deg[i] == 1){
                dfs1(i, -1);
                dfs2(i, -1, 0, 0);
            }
        }
        cout << ans << ' ' << cnt_ans / 2<< endl;
    }
}
main()
{
    fast;
    if (fopen(TASKNAME".inp","r")){
        freopen(TASKNAME".inp","r",stdin);
        freopen(TASKNAME".out","w",stdout);
    }
    cin >> n;
    FOR(i, 1, n - 1){
        cin >> edge[i].fi >> edge[i].se;
        g[edge[i].fi].pb(i);
        g[edge[i].se].pb(i);
    }

    if (subtask2::check()) return subtask2::solve(), 0;


}
/**
Warning:
Đọc sai đề???
Cận lmao
Code imple thiếu case nào không.
Limit.
**/

Compilation message (stderr)

road.cpp:90:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   90 | main()
      | ^~~~
road.cpp: In function 'int main()':
road.cpp:94:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   94 |         freopen(TASKNAME".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
road.cpp:95:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   95 |         freopen(TASKNAME".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 19 / 19
• Subtask 2: 33 / 33
• Subtask 3: 0 / 48