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Submission #424146

# Submission time Handle Problem Language Result Execution time Memory
424146 2021-06-11T17:17:06 Z dolphingarlic The Xana coup (BOI21_xanadu) C++14
30 / 100
 92 ms 21472 KB 
#include <bits/stdc++.h>
typedef long long ll;
using namespace std;

const ll INF = 1e9;

vector<int> graph[100001];
bool white[100001];
ll dp[100001][2][2];

void dfs(int node = 1, int parent = 0) {
    ll case_1 = 0, case_2 = 0;
    ll switch_1 = INF, switch_2 = INF;
    bool parity_1 = !white[node], parity_2 = white[node];
    for (int i : graph[node]) if (i != parent) {
        dfs(i, node);
        // Case 1: We switch node
        if (dp[i][1][0] < dp[i][1][1]) {
            case_1 += dp[i][1][0];
            switch_1 = min(switch_1, dp[i][1][1] - dp[i][1][0]);
        } else {
            case_1 += dp[i][1][1];
            switch_1 = min(switch_1, dp[i][1][0] - dp[i][1][1]);
            parity_1 ^= true;
        }
        // Case 2: We don't switch node
        if (dp[i][0][0] < dp[i][0][1]) {
            case_2 += dp[i][0][0];
            switch_2 = min(switch_2, dp[i][0][1] - dp[i][0][0]);
        } else {
            case_2 += dp[i][0][1];
            switch_2 = min(switch_2, dp[i][0][0] - dp[i][0][1]);
            parity_2 ^= true;
        }
    }
    dp[node][parity_1][1] = case_1 + 1;
    dp[node][!parity_1][1] = dp[node][parity_1][1] + switch_1;
    dp[node][parity_2][0] = case_2;
    dp[node][!parity_2][0] = dp[node][parity_2][0] + switch_2;
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    int n;
    cin >> n;
    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        graph[u].push_back(v);
        graph[v].push_back(u);
    }
    for (int i = 1; i <= n; i++) cin >> white[i];
    dfs();
    int ans = min(dp[1][0][0], dp[1][0][1]);
    if (ans > n) cout << "impossible";
    else cout << ans;
    return 0;
}

Subtask #1
5.0 / 5.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 2636 KB Output is correct
2 Correct 2 ms 2636 KB Output is correct
3 Correct 2 ms 2636 KB Output is correct
4 Correct 2 ms 2636 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct

Subtask #2
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 2636 KB Output is correct
2 Correct 2 ms 2636 KB Output is correct
3 Correct 2 ms 2636 KB Output is correct
4 Correct 2 ms 2636 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct
7 Correct 2 ms 2636 KB Output is correct
8 Correct 2 ms 2636 KB Output is correct
9 Correct 2 ms 2636 KB Output is correct
10 Correct 2 ms 2636 KB Output is correct
11 Correct 2 ms 2636 KB Output is correct
12 Correct 2 ms 2636 KB Output is correct
13 Correct 2 ms 2636 KB Output is correct
14 Correct 2 ms 2636 KB Output is correct
15 Correct 2 ms 2636 KB Output is correct
16 Correct 2 ms 2636 KB Output is correct

Subtask #3
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 79 ms 21384 KB Output is correct
2 Correct 81 ms 21200 KB Output is correct
3 Correct 66 ms 21440 KB Output is correct

Subtask #4
0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 68 ms 21344 KB Output is correct
2 Correct 92 ms 21200 KB Output is correct
3 Correct 77 ms 21472 KB Output is correct
4 Incorrect 60 ms 8340 KB Output isn't correct
5 Halted 0 ms 0 KB -

Subtask #5
0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 2636 KB Output is correct
2 Correct 2 ms 2636 KB Output is correct
3 Correct 2 ms 2636 KB Output is correct
4 Correct 2 ms 2636 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct
7 Correct 2 ms 2636 KB Output is correct
8 Correct 2 ms 2636 KB Output is correct
9 Correct 2 ms 2636 KB Output is correct
10 Correct 2 ms 2636 KB Output is correct
11 Correct 2 ms 2636 KB Output is correct
12 Correct 2 ms 2636 KB Output is correct
13 Correct 2 ms 2636 KB Output is correct
14 Correct 2 ms 2636 KB Output is correct
15 Correct 2 ms 2636 KB Output is correct
16 Correct 2 ms 2636 KB Output is correct
17 Correct 79 ms 21384 KB Output is correct
18 Correct 81 ms 21200 KB Output is correct
19 Correct 66 ms 21440 KB Output is correct
20 Correct 68 ms 21344 KB Output is correct
21 Correct 92 ms 21200 KB Output is correct
22 Correct 77 ms 21472 KB Output is correct
23 Incorrect 60 ms 8340 KB Output isn't correct
24 Halted 0 ms 0 KB -