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Submission #367404

# Submission time Handle Problem Language Result Execution time Memory
367404 2021-02-17T07:40:46 Z dolphingarlic Mousetrap (CEOI17_mousetrap) C++14
100 / 100
 1052 ms 169688 KB 
#include <bits/stdc++.h>
typedef long long ll;
using namespace std;

int n, t, m, c;
vector<int> graph[1000001], chain;
ll dp[1000001], pref[1000001];
bool in_chain[1000001];

bool dfs(int node = t, int parent = 0) {
	ll mx1 = 0, mx2 = 0;
	for (int i : graph[node]) if (i != parent) {
		in_chain[node] |= dfs(i, node);
		if (dp[i] >= mx1) mx2 = mx1, mx1 = dp[i];
		else if (dp[i] > mx2) mx2 = dp[i];
	}
	sort(graph[node].begin(), graph[node].end(), [](int A, int B) { return dp[A] > dp[B]; });
	dp[node] = graph[node].size() - 1 + mx2;
	if (in_chain[node]) chain.push_back(node);
	return in_chain[node];
}

bool check(int mn) {
	int rem = 1, used = 0;
	for (int i = c - 1; i; i--, rem++) {
		int allowed = mn - pref[i] - used;
		for (int j : graph[chain[i]]) if (!in_chain[j]) {
			if (dp[j] <= allowed) break;
			if (!rem) return false;
			rem--, used++;
		}
	}
	return true;
}

int main() {
	cin.tie(0)->sync_with_stdio(0);
	cin >> n >> t >> m;
	for (int i = 1; i < n; i++) {
		int u, v;
		cin >> u >> v;
		graph[u].push_back(v);
		graph[v].push_back(u);
	}
	in_chain[m] = true;
	dfs();
	reverse(chain.begin(), chain.end());
	c = chain.size();
	for (int i = 1; i < c; i++)
		pref[i] = pref[i - 1] + graph[chain[i]].size() - 2 + (i == c - 1);

	int l = pref[c - 1], r = n - 1;
	while (l != r) {
		int mid = (l + r) / 2;
		if (check(mid)) r = mid;
		else l = mid + 1;
	}
	cout << l;
	return 0;
}

Subtask #1
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 15 ms 23788 KB Output is correct
2 Correct 15 ms 23788 KB Output is correct
3 Correct 15 ms 23788 KB Output is correct
4 Correct 15 ms 23788 KB Output is correct
5 Correct 15 ms 23788 KB Output is correct
6 Correct 15 ms 23788 KB Output is correct
7 Correct 18 ms 23788 KB Output is correct
8 Correct 15 ms 23788 KB Output is correct
9 Correct 15 ms 23788 KB Output is correct
10 Correct 15 ms 23788 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 341 ms 63468 KB Output is correct
2 Correct 327 ms 59472 KB Output is correct
3 Correct 988 ms 65004 KB Output is correct
4 Correct 447 ms 44396 KB Output is correct
5 Correct 929 ms 65152 KB Output is correct
6 Correct 908 ms 65004 KB Output is correct

Subtask #3
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 15 ms 23788 KB Output is correct
2 Correct 15 ms 23788 KB Output is correct
3 Correct 15 ms 23788 KB Output is correct
4 Correct 15 ms 23788 KB Output is correct
5 Correct 15 ms 23788 KB Output is correct
6 Correct 15 ms 23788 KB Output is correct
7 Correct 18 ms 23788 KB Output is correct
8 Correct 15 ms 23788 KB Output is correct
9 Correct 15 ms 23788 KB Output is correct
10 Correct 15 ms 23788 KB Output is correct
11 Correct 18 ms 23788 KB Output is correct
12 Correct 18 ms 23916 KB Output is correct
13 Correct 16 ms 23916 KB Output is correct
14 Correct 15 ms 24044 KB Output is correct
15 Correct 16 ms 23916 KB Output is correct
16 Correct 15 ms 23916 KB Output is correct
17 Correct 15 ms 23916 KB Output is correct
18 Correct 16 ms 23916 KB Output is correct
19 Correct 16 ms 23916 KB Output is correct
20 Correct 16 ms 23916 KB Output is correct
21 Correct 16 ms 23916 KB Output is correct
22 Correct 15 ms 23916 KB Output is correct

Subtask #4
35.0 / 35.0

# Verdict Execution time Memory Grader output
1 Correct 15 ms 23788 KB Output is correct
2 Correct 15 ms 23788 KB Output is correct
3 Correct 15 ms 23788 KB Output is correct
4 Correct 15 ms 23788 KB Output is correct
5 Correct 15 ms 23788 KB Output is correct
6 Correct 15 ms 23788 KB Output is correct
7 Correct 18 ms 23788 KB Output is correct
8 Correct 15 ms 23788 KB Output is correct
9 Correct 15 ms 23788 KB Output is correct
10 Correct 15 ms 23788 KB Output is correct
11 Correct 341 ms 63468 KB Output is correct
12 Correct 327 ms 59472 KB Output is correct
13 Correct 988 ms 65004 KB Output is correct
14 Correct 447 ms 44396 KB Output is correct
15 Correct 929 ms 65152 KB Output is correct
16 Correct 908 ms 65004 KB Output is correct
17 Correct 18 ms 23788 KB Output is correct
18 Correct 18 ms 23916 KB Output is correct
19 Correct 16 ms 23916 KB Output is correct
20 Correct 15 ms 24044 KB Output is correct
21 Correct 16 ms 23916 KB Output is correct
22 Correct 15 ms 23916 KB Output is correct
23 Correct 15 ms 23916 KB Output is correct
24 Correct 16 ms 23916 KB Output is correct
25 Correct 16 ms 23916 KB Output is correct
26 Correct 16 ms 23916 KB Output is correct
27 Correct 16 ms 23916 KB Output is correct
28 Correct 15 ms 23916 KB Output is correct
29 Correct 16 ms 23788 KB Output is correct
30 Correct 385 ms 63564 KB Output is correct
31 Correct 350 ms 63508 KB Output is correct
32 Correct 498 ms 169688 KB Output is correct
33 Correct 402 ms 157804 KB Output is correct
34 Correct 922 ms 65260 KB Output is correct
35 Correct 919 ms 65116 KB Output is correct
36 Correct 1000 ms 75876 KB Output is correct
37 Correct 1052 ms 75748 KB Output is correct
38 Correct 813 ms 77668 KB Output is correct
39 Correct 836 ms 77576 KB Output is correct
40 Correct 858 ms 77796 KB Output is correct