Submission #489683

#	Time	Username	Problem	Language	Result	Execution time	Memory
489683		arwaeystoamneg	The Xana coup (BOI21_xanadu)	C++17	100 / 100	66 ms	18472 KiB

xanadu

// EXPLOSION!
#define _CRT_SECURE_NO_WARNINGS
#include<bits/stdc++.h>
#include<unordered_set>
#include<unordered_map>
#include<chrono>

using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pair<int, int>> vpi;
typedef vector<pair<ll, ll>> vpll;

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)

#define pb push_back
#define mp make_pair
#define rsz resize
#define sz(x) int(x.size())
#define all(x) x.begin(),x.end()
#define f first
#define s second
#define cont continue
#define endl '\n'
//#define ednl '\n'
#define test int testc;cin>>testc;while(testc--)
#define pr(a, b) trav(x,a)cerr << x << b; cerr << endl;
#define message cout << "Hello World" << endl;
const int dx[4] = { 1,0,-1,0 }, dy[4] = { 0,1,0,-1 }; // for every grid problem!!
const ll linf = 4000000000000000000LL;
const ll inf = 1000000007;//998244353    

void pv(vi a) { trav(x, a)cout << x << " "; cout << endl; }void pv(vll a) { trav(x, a)cout << x << " "; cout << endl; }void pv(vector<vi>a) {
	F0R(i, sz(a)) { cout << i << endl; pv(a[i]); cout << endl; }
}void pv(vector<vll>a) { F0R(i, sz(a)) { cout << i << endl; pv(a[i]); }cout << endl; }void pv(vector<string>a) { trav(x, a)cout << x << endl; cout << endl; }
void setIO(string s) {
	ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef arwaeystoamneg
	if (sz(s))
	{
		freopen((s + ".in").c_str(), "r", stdin);
		if (s != "test1")
			freopen((s + ".out").c_str(), "w", stdout);
	}
#endif
}
const int MAX = 111111;
int n;
vector<vi>adj;
vi a;
int dp[MAX][2][2];
void dfs(int i, int p = -1)
{
	if (i && sz(adj[i]) == 1)
	{
		dp[i][a[i]][0] = 0;
		dp[i][1 ^ a[i]][1] = 1;
		return;
	}
	trav(x, adj[i])
	{
		if (x == p)continue;
		dfs(x, i);
	}
	// if do not toggle point
	int cost[2] = { inf,inf }, ne[2] = { 0,0 };
	cost[a[i]] = 0;
	trav(x, adj[i])
	{
		if (x == p)continue;
		ne[0] = ne[1] = inf;
		F0R(j, 2)
		{
			ne[j] = min(ne[j], cost[j] + dp[x][0][0]);
			ne[j ^ 1] = min(ne[j ^ 1], cost[j] + dp[x][0][1]);
		}
		cost[0] = ne[0], cost[1] = ne[1];
	}
	dp[i][0][0] = cost[0];
	dp[i][1][0] = cost[1];
	// toggle point
	cost[0] = cost[1] = inf;
	cost[a[i]] = 1;
	trav(x, adj[i])
	{
		if (x == p)continue;
		ne[0] = ne[1] = inf;
		F0R(j, 2)
		{
			ne[j] = min(ne[j], cost[j] + dp[x][1][0]);
			ne[j ^ 1] = min(ne[j ^ 1], cost[j] + dp[x][1][1]);
		}
		cost[0] = ne[0], cost[1] = ne[1];
	}
	dp[i][1][1] = cost[0];
	dp[i][0][1] = cost[1];
}
int main()
{
	setIO("test1"); 
	cin >> n;
	a.rsz(n);
	adj.rsz(n);
	F0R(i, n - 1)
	{
		int x, y;
		cin >> x >> y;
		x--, y--;
		adj[x].pb(y);
		adj[y].pb(x);
	}
	trav(x, a)cin >> x;
	F0R(i, n)dp[i][0][0] = dp[i][0][1] = dp[i][1][0] = dp[i][1][1] = inf;
	dfs(0);
	int ans = min(dp[0][0][0], dp[0][0][1]);
	if (ans > n)cout << "impossible" << endl;
	else cout << ans << endl;
}

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