Submission #729724

#	Time	Username	Problem	Language	Result	Execution time	Memory
729724		Sam_a17	The Xana coup (BOI21_xanadu)	C++17	100 / 100	88 ms	27144 KiB

xanadu

#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
using namespace std;

#ifndef ONLINE_JUDGE
#define dbg(x) cerr << #x <<" "; print(x); cerr << endl;
#else
#define dbg(x)
#endif

#define sz(x) (int)x.size()
#define len(x) (int)x.length()
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define clr(x) (x).clear()
#define uniq(x) x.resize(unique(all(x)) - x.begin());
#define blt __builtin_popcount

#define pb push_back
#define popf pop_front
#define popb pop_back
#define ld long double
#define ll long long

void print(long long t) { cerr << t; }
void print(int t) { cerr << t; }
void print(string t) { cerr << t; }
void print(char t) { cerr << t; }
void print(double t) { cerr << t; }
void print(long double t) { cerr << t; }
void print(unsigned long long t) { cerr << t; }

template <class T, class V> void print(pair <T, V> p);
template <class T> void print(vector <T> v);
template <class T> void print(set <T> v);
template <class T, class V> void print(map <T, V> v);
template <class T> void print(multiset <T> v);
template <class T, class V> void print(T v[], V n) { cerr << "["; for (int i = 0; i < n; i++) { print(v[i]); cerr << " "; } cerr << "]"; }
template <class T, class V> void print(pair <T, V> p) { cerr << "{"; print(p.first); cerr << ","; print(p.second); cerr << "}"; }
template <class T> void print(vector <T> v) { cerr << "[ "; for (T i : v) { print(i); cerr << " "; } cerr << "]"; }
template <class T> void print(set <T> v) { cerr << "[ "; for (T i : v) { print(i); cerr << " "; } cerr << "]"; }
template <class T> void print(multiset <T> v) { cerr << "[ "; for (T i : v) { print(i); cerr << " "; } cerr << "]"; }
template <class T, class V> void print(map <T, V> v) { cerr << "[ "; for (auto i : v) { print(i); cerr << " "; } cerr << "]"; }
template <class T, class V> void print(unordered_map <T, V> v) { cerr << "[ "; for (auto i : v) { print(i); cerr << " "; } cerr << "]"; }
template <class T> void print(deque <T> v) { cerr << "[ "; for (T i : v) { print(i); cerr << " "; } cerr << "]"; }

#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#define nl '\n'

// for random generations
mt19937 myrand(chrono::steady_clock::now().time_since_epoch().count());
// mt19937 myrand(131);

// for grid problems
int dx[8] = { -1,0,1,0,1,-1,1,-1 };
int dy[8] = { 0,1,0,-1,1,1,-1,-1 };

// lowest / (1 << 17) >= 1e5 / (1 << 18) >= 2e5 / (1 << 21) >= 1e6
void fastIO() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr); cout.tie(nullptr);
}
// file in/out
void setIO(string str = "") {
	fastIO();

	if (str == "input") {
		freopen("input.txt", "r", stdin);
		freopen("output.txt", "w", stdout);
	}
	else {
		// freopen("skis.in", "r", stdin);
		// freopen("skis.out", "w", stdout);
	}
}
// Indexed Set  
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const int N = 2e5 + 10, inf = 1e8;
long long dp[N][2][2];
vector<int> adj[N];
int n, a[N];

void dfs(int node, int parent) {
	dp[node][0][a[node]] = 0;
	dp[node][1][a[node] ^ 1] = 1;

	for(auto i: adj[node]) {
		if(i == parent) continue;
		dfs(i, node);

		vector<vector<long long>> new_dp(2, vector<long long> (2, inf));
		if(dp[i][0][0] != inf) {
			new_dp[0][0] = min(new_dp[0][0], dp[node][0][0] + dp[i][0][0]);
			new_dp[0][1] = min(new_dp[0][1], dp[node][0][1] + dp[i][0][0]);
		} 

		if(dp[i][0][1] != inf) {
			new_dp[1][0] = min(new_dp[1][0], dp[node][1][0] + dp[i][0][1]);
			new_dp[1][1] = min(new_dp[1][1], dp[node][1][1] + dp[i][0][1]);
		} 

		if(dp[i][1][0] != inf) {
			new_dp[0][0] = min(new_dp[0][0], dp[node][0][1] + dp[i][1][0]);
			new_dp[0][1] = min(new_dp[0][1], dp[node][0][0] + dp[i][1][0]);
		} 

		if(dp[i][1][1] != inf) {
			new_dp[1][0] = min(new_dp[1][0], dp[node][1][1] + dp[i][1][1]);
			new_dp[1][1] = min(new_dp[1][1], dp[node][1][0] + dp[i][1][1]);
		}


		for(int j = 0; j < 2; j++) {
			for(int k = 0; k < 2; k++) {
				dp[node][j][k] = new_dp[j][k];
			}
		}
	}
}

void solve_() {
	cin >> n;
	for(int i = 1; i <= n - 1; i++) {
		int x, y; cin >> x >> y;
		adj[x].push_back(y);
		adj[y].push_back(x);
	}
	
	for(int i = 1; i <= n; i++) {
		for(int j = 0; j <= 1; j++) {
			for(int k = 0; k <= 1; k++) {
				dp[i][j][k] = inf;
			}
		}
	}

	for(int i = 1; i <= n; i++) {
		cin >> a[i];
	}

	dfs(1, 0);

	long long ans = min(dp[1][0][0], dp[1][1][0]);
	if(ans < inf) {
		cout << ans << '\n';
	} else {
		cout << "impossible" << '\n';
	}
}

int main() {
	setIO();

	auto solve = [&](int test_case)-> void {
		for (int i = 1; i <= test_case; i++) {
			solve_();
		}
	};

	int test_cases = 1;
	// cin >> test_cases;
	solve(test_cases);

	return 0;
}

Compilation message (stderr)

xanadu.cpp: In function 'void setIO(std::string)':
xanadu.cpp:69:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   69 |   freopen("input.txt", "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
xanadu.cpp:70:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   70 |   freopen("output.txt", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 30 / 30