Submission #1250896

#	Time	Username	Problem	Language	Result	Execution time	Memory
1250896		CrabCNH	Cat Exercise (JOI23_ho_t4)	C++20	100 / 100	163 ms	59788 KiB

Main

#include <bits/stdc++.h>

#define task     "BriantheCrab"

#define int    long long
#define pii    pair <int, int>
#define fi     first
#define se     second
#define szf    sizeof
#define sz(s)  (int)((s).size())
#define all(v) (v).begin(), (v).end()

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

using namespace std;

template <class T> void minimize (T &t, T f) {if (t > f) t = f;}
template <class T> void maximize (T &t, T f) {if (t < f) t = f;}

const int maxN = 2e5 + 5;
const int inf = 1e18 + 7;
const int mod = 1e9 + 7;
const int LOG = 20;

// khong tu code thi khong kha len duoc dau

int n;
int p[maxN];
vector <int> adj[maxN];

namespace sub4 {
    const int maxN = 5e3 + 5;
    
    int dp[maxN];
    int mark[maxN];
    
    struct cc {
        int node, val, dis; 
    };
    
    cc find (int u, int par, int d) {
        cc best = {u, p[u], d};
        for (auto v : adj[u]) {
            if (v == par || mark[v]) {
                continue;
            }
            cc nxt = find (v, u, d + 1);
            if (nxt.val > best.val) {
                best = nxt;
            }
        }
        //cout << best.node << '\n';
        return best;
    }
    
    void dfs (int u, int par) {
        mark[u] = 1;
        for (auto v : adj[u]) {
            if (v == par || mark[v]) {
                continue;
            }
            cc nxt = find (v, u, 1);
            dfs (nxt.node, nxt.node);
            //cout << nxt.node << ' ' << nxt.dis << '\n';
            maximize (dp[u], dp[nxt.node] + nxt.dis);
            
        }
    }
    
    void sol () {
        for (int i = 1; i <= n - 1; i ++) {
            int u, v;
            cin >> u >> v;
            adj[u].push_back (v);
            adj[v].push_back (u);
        }
        for (int i = 1; i <= n; i ++) {
            if (p[i] == n) {
                dfs (i, i);
                cout << dp[i];
                return;
            }
        }
    }
}

namespace full {
    
    int up[maxN][LOG + 1];
    int h[maxN];
    
    void dfs (int u, int par) {
        up[u][0] = par;
        for (int k = 1; k < LOG; k ++) {
            up[u][k] = up[up[u][k - 1]][k - 1];
        }
        for (auto v : adj[u]) {
            if (v == par) {
                continue;
            }
            h[v] = h[u] + 1;
            dfs (v, u);
        }
    }
    
    inline int getLca (int u, int v) {
        if (h[u] < h[v]) {
            swap (u, v);
        }
        int k = h[u] - h[v];
        for (int i = 0; (1 << i) <= k; i ++) {
            if ((k >> i) & 1) {
                u = up[u][i];
            }
        }
        if (u == v) {
            return u;
        }
        for (int i = LOG - 1; i >= 0; i --) {
            if (up[u][i] != up[v][i]) {
                u = up[u][i];
                v = up[v][i];
            }
        }
        return up[u][0];
    }
    
    inline int dist (int u, int v) {
        return h[u] + h[v] - 2 * h[getLca (u, v)];
    }
    
    int par[maxN];
    
    int getRoot (int u) {
        if (par[u] == u) {
            return u;
        }
        return (par[u] = getRoot (par[u]));
    }
    
    inline void merge (int u, int v) {
        u = getRoot (u);
        v = getRoot (v);
        if (u == v) {
            return;
        }
        if (u < v) {
            swap (u, v);
        }
        par[v] = u;
        return;
    }
    
    int dp[maxN];
    
    void sol () {
        for (int i = 1; i <= n - 1; i ++) {
            int u, v;
            cin >> u >> v;
            u = p[u];
            v = p[v];
            adj[u].push_back (v);
            adj[v].push_back (u);
            //cout << u << ' ' << v << '\n';
        }
        for (int i = 1; i <= n; i ++) {
            par[i] = i;
        }
        dfs (n, n);
        //cout << getLca (1, 2);
        for (int u = 1; u <= n; u ++) {
            for (auto v : adj[u]) {
                v = getRoot (v);
                if (v < u) {
                    merge (u, v);
                    maximize (dp[u], dp[v] + dist (u, v));
                    //cout << dp[u] << ' ' << dist (u, v) << '\n';
                }
            }
        }
        cout << dp[n];
    }
}

void solve () {
    cin >> n;
    for (int i = 1; i <= n; i ++) {
        cin >> p[i];
    }    
    if (n <= 0) {
        sub4 :: sol ();
    }
    else {
        full :: sol ();
    }
    return;
}

signed main () {
    cin.tie (nullptr) -> sync_with_stdio (false);
    if (fopen (task".inp", "r")) {
        freopen (task".inp", "r", stdin);
        freopen (task".out", "w", stdout);
    }
    int t = 1;
    //cin >> t;
    while (t --) {
        solve ();
    } 
    return 0;
}
// thfv

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:204:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  204 |         freopen (task".inp", "r", stdin);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:205:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  205 |         freopen (task".out", "w", stdout);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26