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Submission #959820

# Submission time Handle Problem Language Result Execution time Memory
959820 2024-04-09T07:21:55 Z josanneo22 The Xana coup (BOI21_xanadu) C++17
100 / 100
 58 ms 20208 KB 
#include <bits/stdc++.h>
using namespace std;
using i64 = long long;

#define L(i,j,k) for(int i=(j);i<=(k);++i)
#define R(i,j,k) for(int i=(j);i>=(k);--i)
#define rep(i, n) L(i, 1, n)
#define all(x) x.begin(),x.end()
#define me(x,a) memset(x,a,sizeof(x))

#include<random>
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int nax = 1E5 + 500;
int N, a[nax], dp[nax][2][2];
vector<int> G[nax];
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr); cout.tie(nullptr);
	
	cin >> N;
	L(i, 1, N - 1) {
		int u, v; cin >> u >> v;
		G[u].push_back(v);
		G[v].push_back(u);
	}
	L(i, 1, N) cin >> a[i];
	function<void(int, int)> dfs = [&](int u, int f) {
		for (auto & v : G[u]) {
			if (v == f) continue;
			dfs(v, u);
		}
		/* each node is only pressed once and we need to pass on info to the parent node
		 * dp[u][A][B] = minimum amount of operations done when we have considered node u
		 * and we have A = whether we have pressed node u and B = have we pressed an odd or even number of buttons
		 */
		for (int press = 0; press < 2; press++) { // do I want to press this button
			for (int par = 0; par < 2; par++) { // whether we want to pass on to the parent
				int even = 0, odd = N + 1;
				for (auto & v : G[u]) {
					if (v == f) continue;
					int _od = min(odd + dp[v][0][press], even + dp[v][1][press]); // either odd + 1 -> even or even + 1 -> odd
					int _ev = min(odd + dp[v][1][press], even + dp[v][0][press]); // opposite way
					swap(_od, odd); swap(_ev, even);
				}
				if (press ^ par ^ a[u]) dp[u][press][par] = odd + press; // press ^ par ^ a[u] == 1, we need to perform an operation
				else dp[u][press][par] = even + press; // otherwise
				
			}
		}
	};
	dfs(1, 1);
	int ans = min(dp[1][1][0], dp[1][0][0]);
	if (ans > N) cout << "impossible\n";
	else cout << ans << '\n';
}

Subtask #1
5.0 / 5.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 4700 KB Output is correct
2 Correct 1 ms 4700 KB Output is correct
3 Correct 1 ms 4696 KB Output is correct
4 Correct 1 ms 4700 KB Output is correct
5 Correct 1 ms 4700 KB Output is correct

Subtask #2
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 4700 KB Output is correct
2 Correct 1 ms 4700 KB Output is correct
3 Correct 1 ms 4696 KB Output is correct
4 Correct 1 ms 4700 KB Output is correct
5 Correct 1 ms 4700 KB Output is correct
6 Correct 1 ms 4696 KB Output is correct
7 Correct 1 ms 4696 KB Output is correct
8 Correct 1 ms 4700 KB Output is correct
9 Correct 1 ms 4700 KB Output is correct
10 Correct 1 ms 4700 KB Output is correct
11 Correct 1 ms 4696 KB Output is correct
12 Correct 2 ms 4696 KB Output is correct
13 Correct 1 ms 4696 KB Output is correct
14 Correct 1 ms 4700 KB Output is correct
15 Correct 1 ms 4752 KB Output is correct
16 Correct 1 ms 4700 KB Output is correct

Subtask #3
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 47 ms 19800 KB Output is correct
2 Correct 39 ms 19584 KB Output is correct
3 Correct 45 ms 20052 KB Output is correct

Subtask #4
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 41 ms 19708 KB Output is correct
2 Correct 58 ms 19520 KB Output is correct
3 Correct 46 ms 20208 KB Output is correct
4 Correct 30 ms 8732 KB Output is correct
5 Correct 33 ms 9048 KB Output is correct
6 Correct 34 ms 9052 KB Output is correct
7 Correct 1 ms 4700 KB Output is correct
8 Correct 15 ms 6236 KB Output is correct
9 Correct 56 ms 9224 KB Output is correct
10 Correct 33 ms 9356 KB Output is correct
11 Correct 39 ms 10080 KB Output is correct
12 Correct 34 ms 10064 KB Output is correct
13 Correct 31 ms 8720 KB Output is correct
14 Correct 32 ms 9052 KB Output is correct

Subtask #5
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 4700 KB Output is correct
2 Correct 1 ms 4700 KB Output is correct
3 Correct 1 ms 4696 KB Output is correct
4 Correct 1 ms 4700 KB Output is correct
5 Correct 1 ms 4700 KB Output is correct
6 Correct 1 ms 4696 KB Output is correct
7 Correct 1 ms 4696 KB Output is correct
8 Correct 1 ms 4700 KB Output is correct
9 Correct 1 ms 4700 KB Output is correct
10 Correct 1 ms 4700 KB Output is correct
11 Correct 1 ms 4696 KB Output is correct
12 Correct 2 ms 4696 KB Output is correct
13 Correct 1 ms 4696 KB Output is correct
14 Correct 1 ms 4700 KB Output is correct
15 Correct 1 ms 4752 KB Output is correct
16 Correct 1 ms 4700 KB Output is correct
17 Correct 47 ms 19800 KB Output is correct
18 Correct 39 ms 19584 KB Output is correct
19 Correct 45 ms 20052 KB Output is correct
20 Correct 41 ms 19708 KB Output is correct
21 Correct 58 ms 19520 KB Output is correct
22 Correct 46 ms 20208 KB Output is correct
23 Correct 30 ms 8732 KB Output is correct
24 Correct 33 ms 9048 KB Output is correct
25 Correct 34 ms 9052 KB Output is correct
26 Correct 1 ms 4700 KB Output is correct
27 Correct 15 ms 6236 KB Output is correct
28 Correct 56 ms 9224 KB Output is correct
29 Correct 33 ms 9356 KB Output is correct
30 Correct 39 ms 10080 KB Output is correct
31 Correct 34 ms 10064 KB Output is correct
32 Correct 31 ms 8720 KB Output is correct
33 Correct 32 ms 9052 KB Output is correct
34 Correct 1 ms 4700 KB Output is correct
35 Correct 1 ms 4700 KB Output is correct
36 Correct 1 ms 4700 KB Output is correct
37 Correct 1 ms 4696 KB Output is correct
38 Correct 2 ms 5188 KB Output is correct
39 Correct 1 ms 4952 KB Output is correct
40 Correct 1 ms 4700 KB Output is correct
41 Correct 1 ms 4952 KB Output is correct
42 Correct 1 ms 4700 KB Output is correct
43 Correct 1 ms 4700 KB Output is correct
44 Correct 1 ms 4700 KB Output is correct
45 Correct 45 ms 19948 KB Output is correct
46 Correct 38 ms 19888 KB Output is correct
47 Correct 38 ms 20052 KB Output is correct
48 Correct 29 ms 8540 KB Output is correct
49 Correct 32 ms 9048 KB Output is correct
50 Correct 34 ms 9052 KB Output is correct
51 Correct 1 ms 4700 KB Output is correct
52 Correct 12 ms 6236 KB Output is correct
53 Correct 34 ms 9252 KB Output is correct
54 Correct 42 ms 9492 KB Output is correct
55 Correct 35 ms 9812 KB Output is correct
56 Correct 45 ms 10016 KB Output is correct
57 Correct 39 ms 8792 KB Output is correct
58 Correct 41 ms 9052 KB Output is correct
59 Correct 12 ms 6236 KB Output is correct
60 Correct 29 ms 8784 KB Output is correct
61 Correct 32 ms 9040 KB Output is correct
62 Correct 34 ms 9300 KB Output is correct
63 Correct 33 ms 9304 KB Output is correct
64 Correct 33 ms 9304 KB Output is correct
65 Correct 29 ms 9556 KB Output is correct
66 Correct 28 ms 9552 KB Output is correct
67 Correct 34 ms 9468 KB Output is correct
68 Correct 33 ms 9536 KB Output is correct
69 Correct 28 ms 9684 KB Output is correct
70 Correct 27 ms 9684 KB Output is correct