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Submission #398693

# Submission time Handle Problem Language Result Execution time Memory
398693 2021-05-04T17:53:46 Z eggag32 The Xana coup (BOI21_xanadu) C++17
100 / 100
 78 ms 16920 KB 
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef vector<int> vi;
#define debug(x) cerr << #x << " " << x << '\n'
#define debug2(x, y) debug(x), debug(y)
#define rep(i, a) for(int i = 0; i < (a); i++)
#define repn(i, a, b) for(int i = (a); i < (b); i++)
#define all(v) v.begin, v.end()
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define sq(x) ((x) * (x))
#define inf 0x3f3f3f3f
const int mxN = 1e5 + 5;

int n;
int c[mxN];
int dp[mxN][2][2];
vi g[mxN];

void dfs(int cur, int prev){
	//dp[node][type: 0 for all 0s, 1 for 1 at root, the rest 0s][flipped]
	int cnt = 0;
	for(int x : g[cur]) if(x != prev){
		cnt++;
		dfs(x, cur);
	}
	if(!cnt){
		if(c[cur]){
			dp[cur][1][0] = 0;
			dp[cur][0][1] = 1;
		}
		else{
			dp[cur][1][1] = 1;
			dp[cur][0][0] = 0;
		}
		return;
	}
	vector<vi> v(2, {0, 0});
	int nm = 0, cst = 0;
	for(int x : g[cur]) if(x != prev){
		if(dp[x][0][0] < dp[x][0][1]){
			cst += dp[x][0][0];
			cst = min(cst, inf);
		}
		else{
			cst += dp[x][0][1];
			cst = min(cst, inf);
			nm++;
		}
	}
	int mn = inf;
	for(int x : g[cur]) if(x != prev){
		if(dp[x][0][0] < dp[x][0][1]){
			mn = min(mn, dp[x][0][1] - dp[x][0][0]);
		}
		else{
			mn = min(mn, dp[x][0][0] - dp[x][0][1]);
		}
	}
	if(nm & 1){
		v[0][1] = cst;
		v[0][0] = min(inf, cst + mn);
	}
	else{
		v[0][0] = cst;
		v[0][1] = min(inf, cst + mn);
	}
	nm = 0, cst = 0;
	for(int x : g[cur]) if(x != prev){
		if(dp[x][1][0] < dp[x][1][1]){
			cst += dp[x][1][0];
			cst = min(cst, inf);
		}
		else{
			cst += dp[x][1][1];
			cst = min(cst, inf);
			nm++;
		}
	}
	mn = inf;
	for(int x : g[cur]) if(x != prev){
		if(dp[x][1][0] < dp[x][1][1]){
			mn = min(mn, dp[x][1][1] - dp[x][1][0]);
		}
		else{
			mn = min(mn, dp[x][1][0] - dp[x][1][1]);
		}
	}
	if(nm & 1){
		v[1][1] = cst;
		v[1][0] = min(inf, cst + mn);
	}
	else{
		v[1][0] = cst;
		v[1][1] = min(inf, cst + mn);
	}
	if(c[cur]){
		dp[cur][0][1] = 1 + v[1][0];
		dp[cur][0][0] = v[0][1];
	}
	else{
		dp[cur][0][1] = 1 + v[1][1];
		dp[cur][0][0] = v[0][0];
	}
	if(c[cur]){
		dp[cur][1][1] = 1 + v[1][1];
		dp[cur][1][0] = v[0][0];
	}
	else{
		dp[cur][1][1] = 1 + v[1][0];
		dp[cur][1][0] = v[0][1];
	}
}

int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin >> n;
	memset(dp, inf, sizeof(dp));
	rep(i, n - 1){
		int a, b;
		cin >> a >> b;
		a--, b--;
		g[a].pb(b);
		g[b].pb(a);
	}
	rep(i, n) cin >> c[i];
	dfs(0, -1);	
	int ans = min(dp[0][0][0], dp[0][0][1]);
	if(ans >= 1e9) cout << "impossible\n";
	else cout << ans << '\n';
}

Subtask #1
5.0 / 5.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 4172 KB Output is correct
2 Correct 3 ms 4172 KB Output is correct
3 Correct 3 ms 4172 KB Output is correct
4 Correct 3 ms 4172 KB Output is correct
5 Correct 3 ms 4208 KB Output is correct

Subtask #2
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 4172 KB Output is correct
2 Correct 3 ms 4172 KB Output is correct
3 Correct 3 ms 4172 KB Output is correct
4 Correct 3 ms 4172 KB Output is correct
5 Correct 3 ms 4208 KB Output is correct
6 Correct 3 ms 4172 KB Output is correct
7 Correct 3 ms 4212 KB Output is correct
8 Correct 3 ms 4172 KB Output is correct
9 Correct 3 ms 4172 KB Output is correct
10 Correct 2 ms 4172 KB Output is correct
11 Correct 3 ms 4172 KB Output is correct
12 Correct 3 ms 4172 KB Output is correct
13 Correct 3 ms 4176 KB Output is correct
14 Correct 3 ms 4172 KB Output is correct
15 Correct 3 ms 4172 KB Output is correct
16 Correct 3 ms 4300 KB Output is correct

Subtask #3
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 66 ms 16788 KB Output is correct
2 Correct 76 ms 16580 KB Output is correct
3 Correct 78 ms 16920 KB Output is correct

Subtask #4
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 70 ms 16836 KB Output is correct
2 Correct 69 ms 16836 KB Output is correct
3 Correct 68 ms 16836 KB Output is correct
4 Correct 66 ms 8556 KB Output is correct
5 Correct 71 ms 9064 KB Output is correct
6 Correct 69 ms 8984 KB Output is correct
7 Correct 3 ms 4172 KB Output is correct
8 Correct 27 ms 5836 KB Output is correct
9 Correct 68 ms 9028 KB Output is correct
10 Correct 70 ms 9156 KB Output is correct
11 Correct 73 ms 9580 KB Output is correct
12 Correct 71 ms 9800 KB Output is correct
13 Correct 57 ms 8772 KB Output is correct
14 Correct 73 ms 9036 KB Output is correct

Subtask #5
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 4172 KB Output is correct
2 Correct 3 ms 4172 KB Output is correct
3 Correct 3 ms 4172 KB Output is correct
4 Correct 3 ms 4172 KB Output is correct
5 Correct 3 ms 4208 KB Output is correct
6 Correct 3 ms 4172 KB Output is correct
7 Correct 3 ms 4212 KB Output is correct
8 Correct 3 ms 4172 KB Output is correct
9 Correct 3 ms 4172 KB Output is correct
10 Correct 2 ms 4172 KB Output is correct
11 Correct 3 ms 4172 KB Output is correct
12 Correct 3 ms 4172 KB Output is correct
13 Correct 3 ms 4176 KB Output is correct
14 Correct 3 ms 4172 KB Output is correct
15 Correct 3 ms 4172 KB Output is correct
16 Correct 3 ms 4300 KB Output is correct
17 Correct 66 ms 16788 KB Output is correct
18 Correct 76 ms 16580 KB Output is correct
19 Correct 78 ms 16920 KB Output is correct
20 Correct 70 ms 16836 KB Output is correct
21 Correct 69 ms 16836 KB Output is correct
22 Correct 68 ms 16836 KB Output is correct
23 Correct 66 ms 8556 KB Output is correct
24 Correct 71 ms 9064 KB Output is correct
25 Correct 69 ms 8984 KB Output is correct
26 Correct 3 ms 4172 KB Output is correct
27 Correct 27 ms 5836 KB Output is correct
28 Correct 68 ms 9028 KB Output is correct
29 Correct 70 ms 9156 KB Output is correct
30 Correct 73 ms 9580 KB Output is correct
31 Correct 71 ms 9800 KB Output is correct
32 Correct 57 ms 8772 KB Output is correct
33 Correct 73 ms 9036 KB Output is correct
34 Correct 3 ms 4172 KB Output is correct
35 Correct 3 ms 4172 KB Output is correct
36 Correct 3 ms 4212 KB Output is correct
37 Correct 3 ms 4172 KB Output is correct
38 Correct 3 ms 4236 KB Output is correct
39 Correct 3 ms 4172 KB Output is correct
40 Correct 3 ms 4188 KB Output is correct
41 Correct 4 ms 4212 KB Output is correct
42 Correct 3 ms 4172 KB Output is correct
43 Correct 3 ms 4172 KB Output is correct
44 Correct 3 ms 4172 KB Output is correct
45 Correct 71 ms 16772 KB Output is correct
46 Correct 66 ms 16580 KB Output is correct
47 Correct 71 ms 16868 KB Output is correct
48 Correct 63 ms 8564 KB Output is correct
49 Correct 70 ms 8920 KB Output is correct
50 Correct 74 ms 9080 KB Output is correct
51 Correct 3 ms 4212 KB Output is correct
52 Correct 24 ms 5964 KB Output is correct
53 Correct 68 ms 8972 KB Output is correct
54 Correct 67 ms 9176 KB Output is correct
55 Correct 71 ms 9524 KB Output is correct
56 Correct 70 ms 9796 KB Output is correct
57 Correct 61 ms 8776 KB Output is correct
58 Correct 68 ms 9136 KB Output is correct
59 Correct 21 ms 5828 KB Output is correct
60 Correct 63 ms 8620 KB Output is correct
61 Correct 66 ms 9044 KB Output is correct
62 Correct 71 ms 9184 KB Output is correct
63 Correct 69 ms 9100 KB Output is correct
64 Correct 69 ms 9052 KB Output is correct
65 Correct 51 ms 9576 KB Output is correct
66 Correct 56 ms 9592 KB Output is correct
67 Correct 48 ms 9456 KB Output is correct
68 Correct 46 ms 9400 KB Output is correct
69 Correct 45 ms 9404 KB Output is correct
70 Correct 48 ms 9452 KB Output is correct