Submission #1312991

#	Time	Username	Problem	Language	Result	Execution time	Memory
1312991		lev	Forensic (NOI12_forensic)	C++20	0 / 25	2 ms	2360 KiB

forensic

#include <bits/stdc++.h>
// Kazusa_Megumi
#define ll long long
#define fi first
#define se second
#define pii pair<int, int>
#define all(a) a.begin(), a.end()
using namespace std;

#ifdef LOCAL
#include "C:\Users\Dell\Downloads\template\template\icpc-notebook\Utilities\debug.h"
#else
#define debug(...) 42
#endif

const int mn = 5e5 + 5, mod = 1e9 + 7, inf = 2e9;

int n, nxt[mn], vis[mn], dp[mn], cnt = 0, loop = 0;

void down(int u){
	vis[u] = 1, dp[u] = 0;
	cnt ++;

	if(nxt[u] == -1) return;
	if(vis[nxt[u]]){
		loop = 1;
		return;
	}

	down(nxt[u]);
}

int f(int u){
	if(nxt[u] == -1) return 1;
	if((vis[nxt[u]] && loop) || u == 1) return - 1e9;
	if(dp[u] != -1) return dp[u];
	dp[u] = 0;
	if(vis[u] == 1) return dp[u] = - 1e9;
	vis[u] = 1;
	dp[u] = f(nxt[u]) + 1;
	vis[u] = 2;
	return dp[u];
}

void solve() {
 	cin >> n;
 	for(int i = 1; i <= n; i++){
 		cin >> nxt[i];
 		if(nxt[i] != -1) nxt[i] ++;
 	}
 	down(1);
 	memset(dp, -1, sizeof(dp));
 	int ans = - 1e9;
 	for(int i = 1; i <= n; i++){
 		if(!vis[i]){
 			debug(i, f(i));
 			ans = max(ans, f(i));
 		}
 	}
 	cout << ans + cnt << '\n';
}

main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
    if (fopen("Kazuki.INP", "r")) {
        freopen("Kazuki.INP", "r", stdin);
        freopen("Kazuki.OUT", "w", stdout);
    }
    int t = 1;
    // cin >> t;
    while (t--) solve();
    return 0;
}

Compilation message (stderr)

forensic.cpp:63:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   63 | main() {
      | ^~~~
forensic.cpp: In function 'int main()':
forensic.cpp:67:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   67 |         freopen("Kazuki.INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
forensic.cpp:68:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   68 |         freopen("Kazuki.OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 5
• Subtask 3: 0 / 5
• Subtask 4: 0 / 10