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Submission #401963

# Submission time Handle Problem Language Result Execution time Memory
401963 2021-05-11T05:02:59 Z blue The Xana coup (BOI21_xanadu) C++17
100 / 100
 178 ms 22716 KB 
#include <iostream>
#include <vector>
using namespace std;

/*
dp[u][flag1][flag2] = minimum toggles from descendants of u only required such that:
                        state of u is flag1
                        state of all direct children of u is flag2
                        state of all other descendants is 0.

              if this is impossible, 1e9;
*/

vector<int> edge[100001];
int sv[100001];

vector<int> p(100001, 0);
vector<int> children[100001];

int dp[100001][2][2];


void dfs1(int u)
{
    for(int v: edge[u])
    {
        if(p[u] == v) continue;

        p[v] = u;
        children[u].push_back(v);

        dfs1(v);
    }
}

void dfs2(int u)
{
    for(int v: children[u])
        dfs2(v);

    dp[u][ sv[u] ][0] = dp[u][ sv[u] ][1] = 0;

    //dp_curr[u][flag1][flag2] = state of dp assuming it has only previously visited children

    for(int v: children[u])
    {
        int X[2][2];

        for(int f = 0; f <= 1; f++)
            for(int g = 0; g <= 1; g++)
                X[f][g] = min(dp[u][f][g] + dp[v][g][0], dp[u][!f][g] + dp[v][!g][1] + 1);

        for(int f = 0; f <= 1; f++)
            for(int g = 0; g <= 1; g++)
                dp[u][f][g] = X[f][g];
    }

    // cout << u << ' ' << dp[u][0][0] << ' ' << dp[u][0][1] << ' ' << dp[u][1][0] << ' ' << dp[u][1][1] << '\n';
}

int main()
{
    int N;
    cin >> N;

    for(int i = 1; i <= N-1; i++)
    {
        int a, b;
        cin >> a >> b;
        edge[a].push_back(b);
        edge[b].push_back(a);
    }

    edge[1].push_back(0);
    edge[0].push_back(1);

    dfs1(0);

    for(int i = 0; i <= N; i++)
    {
        for(int f = 0; f <= 1; f++)
            for(int g = 0; g <= 1; g++)
                dp[i][f][g] = N+1;
    }

    for(int i = 1; i <= N; i++)
        cin >> sv[i];

    dp[0][0][0] = dp[0][0][1] = dp[0][1][0] = dp[0][1][1] = 0;
    dfs2(0);

    int res = min(dp[0][0][0], dp[0][1][0]);
    if(res >= N+1) cout << "impossible\n";
    else cout << res << '\n';
}

Subtask #1
5.0 / 5.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 5324 KB Output is correct
2 Correct 4 ms 5452 KB Output is correct
3 Correct 3 ms 5408 KB Output is correct
4 Correct 4 ms 5324 KB Output is correct
5 Correct 10 ms 5324 KB Output is correct

Subtask #2
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 5324 KB Output is correct
2 Correct 4 ms 5452 KB Output is correct
3 Correct 3 ms 5408 KB Output is correct
4 Correct 4 ms 5324 KB Output is correct
5 Correct 10 ms 5324 KB Output is correct
6 Correct 3 ms 5324 KB Output is correct
7 Correct 4 ms 5324 KB Output is correct
8 Correct 3 ms 5324 KB Output is correct
9 Correct 3 ms 5324 KB Output is correct
10 Correct 3 ms 5416 KB Output is correct
11 Correct 4 ms 5324 KB Output is correct
12 Correct 4 ms 5412 KB Output is correct
13 Correct 4 ms 5324 KB Output is correct
14 Correct 3 ms 5324 KB Output is correct
15 Correct 3 ms 5404 KB Output is correct
16 Correct 3 ms 5408 KB Output is correct

Subtask #3
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 127 ms 22568 KB Output is correct
2 Correct 138 ms 22656 KB Output is correct
3 Correct 133 ms 22680 KB Output is correct

Subtask #4
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 126 ms 22596 KB Output is correct
2 Correct 121 ms 22476 KB Output is correct
3 Correct 147 ms 22716 KB Output is correct
4 Correct 114 ms 12784 KB Output is correct
5 Correct 137 ms 13568 KB Output is correct
6 Correct 147 ms 13664 KB Output is correct
7 Correct 4 ms 5324 KB Output is correct
8 Correct 43 ms 8288 KB Output is correct
9 Correct 136 ms 14088 KB Output is correct
10 Correct 148 ms 14124 KB Output is correct
11 Correct 151 ms 14580 KB Output is correct
12 Correct 152 ms 14932 KB Output is correct
13 Correct 117 ms 12808 KB Output is correct
14 Correct 159 ms 13272 KB Output is correct

Subtask #5
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 5324 KB Output is correct
2 Correct 4 ms 5452 KB Output is correct
3 Correct 3 ms 5408 KB Output is correct
4 Correct 4 ms 5324 KB Output is correct
5 Correct 10 ms 5324 KB Output is correct
6 Correct 3 ms 5324 KB Output is correct
7 Correct 4 ms 5324 KB Output is correct
8 Correct 3 ms 5324 KB Output is correct
9 Correct 3 ms 5324 KB Output is correct
10 Correct 3 ms 5416 KB Output is correct
11 Correct 4 ms 5324 KB Output is correct
12 Correct 4 ms 5412 KB Output is correct
13 Correct 4 ms 5324 KB Output is correct
14 Correct 3 ms 5324 KB Output is correct
15 Correct 3 ms 5404 KB Output is correct
16 Correct 3 ms 5408 KB Output is correct
17 Correct 127 ms 22568 KB Output is correct
18 Correct 138 ms 22656 KB Output is correct
19 Correct 133 ms 22680 KB Output is correct
20 Correct 126 ms 22596 KB Output is correct
21 Correct 121 ms 22476 KB Output is correct
22 Correct 147 ms 22716 KB Output is correct
23 Correct 114 ms 12784 KB Output is correct
24 Correct 137 ms 13568 KB Output is correct
25 Correct 147 ms 13664 KB Output is correct
26 Correct 4 ms 5324 KB Output is correct
27 Correct 43 ms 8288 KB Output is correct
28 Correct 136 ms 14088 KB Output is correct
29 Correct 148 ms 14124 KB Output is correct
30 Correct 151 ms 14580 KB Output is correct
31 Correct 152 ms 14932 KB Output is correct
32 Correct 117 ms 12808 KB Output is correct
33 Correct 159 ms 13272 KB Output is correct
34 Correct 3 ms 5324 KB Output is correct
35 Correct 3 ms 5404 KB Output is correct
36 Correct 4 ms 5400 KB Output is correct
37 Correct 3 ms 5324 KB Output is correct
38 Correct 4 ms 5408 KB Output is correct
39 Correct 4 ms 5324 KB Output is correct
40 Correct 4 ms 5324 KB Output is correct
41 Correct 4 ms 5324 KB Output is correct
42 Correct 3 ms 5324 KB Output is correct
43 Correct 4 ms 5324 KB Output is correct
44 Correct 3 ms 5404 KB Output is correct
45 Correct 122 ms 22596 KB Output is correct
46 Correct 129 ms 22404 KB Output is correct
47 Correct 130 ms 22708 KB Output is correct
48 Correct 117 ms 12856 KB Output is correct
49 Correct 134 ms 13508 KB Output is correct
50 Correct 141 ms 13692 KB Output is correct
51 Correct 4 ms 5324 KB Output is correct
52 Correct 42 ms 8308 KB Output is correct
53 Correct 147 ms 14072 KB Output is correct
54 Correct 132 ms 14148 KB Output is correct
55 Correct 139 ms 14688 KB Output is correct
56 Correct 154 ms 14860 KB Output is correct
57 Correct 136 ms 12868 KB Output is correct
58 Correct 131 ms 13364 KB Output is correct
59 Correct 41 ms 8132 KB Output is correct
60 Correct 124 ms 12876 KB Output is correct
61 Correct 131 ms 13696 KB Output is correct
62 Correct 178 ms 13824 KB Output is correct
63 Correct 133 ms 13832 KB Output is correct
64 Correct 139 ms 13880 KB Output is correct
65 Correct 129 ms 12856 KB Output is correct
66 Correct 127 ms 12800 KB Output is correct
67 Correct 107 ms 12636 KB Output is correct
68 Correct 107 ms 12736 KB Output is correct
69 Correct 108 ms 12736 KB Output is correct
70 Correct 110 ms 12724 KB Output is correct