#include <bits/stdc++.h>
using namespace std;
#define int long long
const int maxn = 1E5+5;
const int INF = 1E9;
int n, dp[maxn][2][2], b[maxn]; // colours AFTER flipping, times flipped
bool cn[maxn][2][2];
vector<int> adj[maxn];
void dfs(int u, int p) {
// cout << u << " " << p << endl;
for (int i = 0; i < 2; i++) for (int j = 0; j < 2; j++) {
dp[u][i][j] = INF;
}
// int one[2][2];
// for (int i = 0; i < 2; i++) {
// for (int j = 0; j < 2; j++) {
// cn[u][i][j] = (b[u] == (i ^ j));
// one[i][j] = 0;
// }
// }
int child = 0;
for (int v : adj[u]) {
if (v == p) continue;
dfs(v, u);
child++;
// cn[u][0][0] = (cn[u][0][0] & cn[v][0][0]);
// cn[u][1][0] = (cn[u][1][0] & cn[v][0][0]);
// cn[u][0][1] = (cn[u][0][1] & cn[v][1][0]);
// cn[u][1][1] = (cn[u][1][1] & cn[v][1][0]);
}
// for (int i = 0; i < 2; i++) {
// for (int j = 0; j < 2; j++) {
// if (!cn[u][i][j]) continue;
// for (int v : adj[u]) {
// if (v == p) continue;
// dp[u][i][j] += dp[v][j][0] + j;
// }
// }
// }
for (int k = 0; k < 2; k++) {
int i = 0, one[2][2];
one[0][0] = one[1][0] = 0;
one[0][1] = one[1][1] = INF;
for (int v : adj[u]) {
if (v == p) continue;
one[i][0] = min({one[i ^ 1][1] + dp[v][k][1], one[i ^ 1][0] + dp[v][k][0]});
one[i][1] = min({one[i ^ 1][0] + dp[v][k][1], one[i ^ 1][1] + dp[v][k][0]});
// cout << "ones: " << one[i][0] << " " << one[i][1] << "\n";
i = i ^ 1;
}
// cout << (i ^ 1) << " " << k << " " << one[0][0] << " " << one[0][1] << " " << one[1][0] << " " << one[1][1] << "\n";
// cout << (i ^ 1) << " " << (b[u] ^ k) << endl;
dp[u][b[u] ^ k][k] = min(dp[u][b[u] ^ k][k], one[i ^ 1][0]);
dp[u][b[u] ^ 1 ^ k][k] = min(dp[u][b[u] ^ 1 ^ k][k], one[i ^ 1][1]);
}
dp[u][0][1]++, dp[u][1][1]++;
// for (int i = 0; i < 2; i++) {
// for (int j = 0; j < 2; j++) {
// if (b[u] != (i ^ j)) dp[u][i][j] = INF;
// }
// }
// cout << u << endl;
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 2; j++) {
// cout << ((i == 0) ? "off " : "on ") <<((j == 0) ? "noflip " : "flip ") << dp[u][i][j] << ' ';
}
// cout << '\n';
}
}
int32_t main() {
ios::sync_with_stdio(0); cin.tie(0);
cin >> n;
for (int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for (int i = 1; i <= n; i++) cin >> b[i];
dfs(1, 0);
int mn = 1E18;
for (int j = 0; j < 2; j++) {
mn = min(mn, dp[1][0][j]);
}
if (mn > n) cout << "impossible\n";
else cout << mn << endl;
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
2644 KB |
Output is correct |
2 |
Correct |
2 ms |
2644 KB |
Output is correct |
3 |
Correct |
2 ms |
2644 KB |
Output is correct |
4 |
Correct |
1 ms |
2644 KB |
Output is correct |
5 |
Correct |
1 ms |
2680 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
2644 KB |
Output is correct |
2 |
Correct |
2 ms |
2644 KB |
Output is correct |
3 |
Correct |
2 ms |
2644 KB |
Output is correct |
4 |
Correct |
1 ms |
2644 KB |
Output is correct |
5 |
Correct |
1 ms |
2680 KB |
Output is correct |
6 |
Correct |
1 ms |
2644 KB |
Output is correct |
7 |
Correct |
2 ms |
2680 KB |
Output is correct |
8 |
Correct |
1 ms |
2684 KB |
Output is correct |
9 |
Correct |
1 ms |
2644 KB |
Output is correct |
10 |
Correct |
1 ms |
2644 KB |
Output is correct |
11 |
Correct |
2 ms |
2772 KB |
Output is correct |
12 |
Correct |
1 ms |
2644 KB |
Output is correct |
13 |
Correct |
2 ms |
2684 KB |
Output is correct |
14 |
Correct |
1 ms |
2644 KB |
Output is correct |
15 |
Correct |
1 ms |
2644 KB |
Output is correct |
16 |
Correct |
1 ms |
2644 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
39 ms |
23468 KB |
Output is correct |
2 |
Correct |
37 ms |
23112 KB |
Output is correct |
3 |
Correct |
45 ms |
23496 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
38 ms |
23424 KB |
Output is correct |
2 |
Correct |
44 ms |
23244 KB |
Output is correct |
3 |
Correct |
38 ms |
23500 KB |
Output is correct |
4 |
Correct |
31 ms |
10856 KB |
Output is correct |
5 |
Correct |
39 ms |
11696 KB |
Output is correct |
6 |
Correct |
40 ms |
11836 KB |
Output is correct |
7 |
Correct |
2 ms |
2644 KB |
Output is correct |
8 |
Correct |
12 ms |
5648 KB |
Output is correct |
9 |
Correct |
35 ms |
11520 KB |
Output is correct |
10 |
Correct |
37 ms |
11744 KB |
Output is correct |
11 |
Correct |
35 ms |
12280 KB |
Output is correct |
12 |
Correct |
36 ms |
12620 KB |
Output is correct |
13 |
Correct |
42 ms |
11600 KB |
Output is correct |
14 |
Correct |
37 ms |
12244 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
2644 KB |
Output is correct |
2 |
Correct |
2 ms |
2644 KB |
Output is correct |
3 |
Correct |
2 ms |
2644 KB |
Output is correct |
4 |
Correct |
1 ms |
2644 KB |
Output is correct |
5 |
Correct |
1 ms |
2680 KB |
Output is correct |
6 |
Correct |
1 ms |
2644 KB |
Output is correct |
7 |
Correct |
2 ms |
2680 KB |
Output is correct |
8 |
Correct |
1 ms |
2684 KB |
Output is correct |
9 |
Correct |
1 ms |
2644 KB |
Output is correct |
10 |
Correct |
1 ms |
2644 KB |
Output is correct |
11 |
Correct |
2 ms |
2772 KB |
Output is correct |
12 |
Correct |
1 ms |
2644 KB |
Output is correct |
13 |
Correct |
2 ms |
2684 KB |
Output is correct |
14 |
Correct |
1 ms |
2644 KB |
Output is correct |
15 |
Correct |
1 ms |
2644 KB |
Output is correct |
16 |
Correct |
1 ms |
2644 KB |
Output is correct |
17 |
Correct |
39 ms |
23468 KB |
Output is correct |
18 |
Correct |
37 ms |
23112 KB |
Output is correct |
19 |
Correct |
45 ms |
23496 KB |
Output is correct |
20 |
Correct |
38 ms |
23424 KB |
Output is correct |
21 |
Correct |
44 ms |
23244 KB |
Output is correct |
22 |
Correct |
38 ms |
23500 KB |
Output is correct |
23 |
Correct |
31 ms |
10856 KB |
Output is correct |
24 |
Correct |
39 ms |
11696 KB |
Output is correct |
25 |
Correct |
40 ms |
11836 KB |
Output is correct |
26 |
Correct |
2 ms |
2644 KB |
Output is correct |
27 |
Correct |
12 ms |
5648 KB |
Output is correct |
28 |
Correct |
35 ms |
11520 KB |
Output is correct |
29 |
Correct |
37 ms |
11744 KB |
Output is correct |
30 |
Correct |
35 ms |
12280 KB |
Output is correct |
31 |
Correct |
36 ms |
12620 KB |
Output is correct |
32 |
Correct |
42 ms |
11600 KB |
Output is correct |
33 |
Correct |
37 ms |
12244 KB |
Output is correct |
34 |
Correct |
2 ms |
2672 KB |
Output is correct |
35 |
Correct |
1 ms |
2644 KB |
Output is correct |
36 |
Correct |
1 ms |
2644 KB |
Output is correct |
37 |
Correct |
1 ms |
2644 KB |
Output is correct |
38 |
Correct |
1 ms |
2676 KB |
Output is correct |
39 |
Correct |
2 ms |
2644 KB |
Output is correct |
40 |
Correct |
2 ms |
2644 KB |
Output is correct |
41 |
Correct |
1 ms |
2644 KB |
Output is correct |
42 |
Correct |
2 ms |
2644 KB |
Output is correct |
43 |
Correct |
2 ms |
2644 KB |
Output is correct |
44 |
Correct |
2 ms |
2644 KB |
Output is correct |
45 |
Correct |
48 ms |
23352 KB |
Output is correct |
46 |
Correct |
36 ms |
23116 KB |
Output is correct |
47 |
Correct |
44 ms |
23564 KB |
Output is correct |
48 |
Correct |
36 ms |
10944 KB |
Output is correct |
49 |
Correct |
36 ms |
11628 KB |
Output is correct |
50 |
Correct |
39 ms |
11940 KB |
Output is correct |
51 |
Correct |
2 ms |
2644 KB |
Output is correct |
52 |
Correct |
15 ms |
5648 KB |
Output is correct |
53 |
Correct |
40 ms |
11468 KB |
Output is correct |
54 |
Correct |
42 ms |
11724 KB |
Output is correct |
55 |
Correct |
36 ms |
12280 KB |
Output is correct |
56 |
Correct |
36 ms |
12620 KB |
Output is correct |
57 |
Correct |
34 ms |
11636 KB |
Output is correct |
58 |
Correct |
39 ms |
12236 KB |
Output is correct |
59 |
Correct |
13 ms |
5656 KB |
Output is correct |
60 |
Correct |
32 ms |
10596 KB |
Output is correct |
61 |
Correct |
35 ms |
11476 KB |
Output is correct |
62 |
Correct |
35 ms |
11664 KB |
Output is correct |
63 |
Correct |
35 ms |
11676 KB |
Output is correct |
64 |
Correct |
35 ms |
11564 KB |
Output is correct |
65 |
Correct |
41 ms |
12116 KB |
Output is correct |
66 |
Correct |
33 ms |
12076 KB |
Output is correct |
67 |
Correct |
30 ms |
11852 KB |
Output is correct |
68 |
Correct |
32 ms |
11864 KB |
Output is correct |
69 |
Correct |
28 ms |
11748 KB |
Output is correct |
70 |
Correct |
33 ms |
11784 KB |
Output is correct |