Submission #331713

#	Time	Username	Problem	Language	Result	Execution time	Memory
331713		ncduy0303	Forensic (NOI12_forensic)	C++17	25 / 25	3 ms	756 KiB

forensic

#include <bits/stdc++.h>

using namespace std;

#define ar array
#define ll long long

const int MAX_N = 2e4 + 1;
const int MOD = 1e9 + 7;
const int INF = 1e9;
const ll LINF = 1e18;

int n, nxt[MAX_N], vis[MAX_N], dp[MAX_N], s_chain, m_chain;
bool cycle;
vector<int> adj;

void dfs(int u) {
    if (u == -1) return;
    if (vis[u]) {
        cycle = true;
        return;
    }
    vis[u] = 1;
    dp[u] = 0;
    s_chain++;
    dfs(nxt[u]);
}

int dfs2(int u) {
    if (u == -1) return 0;
    if (u == 0 || (vis[u] == 1 && cycle)) return -INF;
    if (dp[u] != -1) return dp[u];
    if (vis[u] == 2) return -INF;
    vis[u] = 2;
    return dp[u] = dfs2(nxt[u]) + 1;
}

void solve() {
    cin >> n;
    for (int i = 0; i < n; i++) cin >> nxt[i];
    if (nxt[0] == 0) {
        cout << 1 << "\n";
        return;
    }
    memset(dp, -1, sizeof dp);
    dfs(0);
    for (int i = 0; i < n; i++) {
        if (!vis[i]) {
            m_chain = max(m_chain, dfs2(i));
        }
    }
    cout << s_chain + m_chain << "\n";
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);

    int tc; tc = 1;
    for (int t = 1; t <= tc; t++) {
        // cout << "Case #" << t  << ": ";
        solve();
    }
}

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 5 / 5
• Subtask 4: 10 / 10