Submission #1083969

#	Time	Username	Problem	Language	Result	Execution time	Memory
1083969		steveonalex	The Xana coup (BOI21_xanadu)	C++17	100 / 100	47 ms	29584 KiB

xanadu

#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef unsigned long long ull;
 
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
#define block_of_code if(true)
 
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll lcm(ll a, ll b){return a / gcd(a, b) * b;}
 
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
 
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
double rngesus_d(double l, double r){
    double cur = rngesus(0, MASK(60) - 1);
    cur /= MASK(60) - 1;
    return l + cur * (r - l);
}
 
template <class T1, class T2>
    bool maximize(T1 &a, T2 b){
        if (a < b) {a = b; return true;}
        return false;
    }
 
template <class T1, class T2>
    bool minimize(T1 &a, T2 b){
        if (a > b) {a = b; return true;}
        return false;
    }
 
template <class T>
    void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
        for(auto item: container) out << item << separator;
        out << finish;
    }
 
template <class T>
    void remove_dup(vector<T> &a){
        sort(ALL(a));
        a.resize(unique(ALL(a)) - a.begin());
    }

const int N = 1e5 + 69;
const int INF = 1e9 + 69;

int n; 
vector<int> graph[N];
int initial_state[N];
int dp[N][2][2];

void dfs(int u, int p){
    vector<int> child;
    for(int v: graph[u]) if (v != p){
        child.push_back(v);
        dfs(v, u);
    }

    dp[u][initial_state[u]][0] = 0;
    dp[u][initial_state[u] ^ 1][1] = 1;

    for(int v: child){
        int f[2][2];
        fill(f[0], f[1] + 2, INF);
        // all child is colored 0
        for(int x = 0; x <= 1; ++x) for(int y = 0; y<=1; ++y) for(int z = 0; z <= 1; ++z)
            minimize(f[x ^ y][z], dp[u][x][z] + dp[v][z][y]);

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

    // cout << "ver: " << u << "\n";
    // for(int x = 0; x <= 1; ++x){
    //     for(int y = 0; y<=1; ++y) cout << dp[u][x][y] << " ";
    //     cout << "\n";
    // }
}

int main(void){
    ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);
    clock_t start = clock();

    cin >> n;
    for(int i = 1; i<n; ++i){
        int u, v; cin >> u >> v;
        graph[u].push_back(v);
        graph[v].push_back(u);
    }

    for(int i = 1; i<=n; ++i) cin >> initial_state[i];

    for(int i = 1; i<=n; ++i) for(int x = 0; x <= 1; ++x) for(int y = 0; y <= 1; ++y) dp[i][x][y] = INF;
    dfs(1, 0);

    int ans = INF;
    for(int i = 0; i <= 1; ++i) minimize(ans, dp[1][0][i]);

    if (ans == INF) cout << "impossible\n";
    else cout << ans << "\n";

    cerr << "Time elapsed: " << clock() - start << " ms\n";
    return 0;
}

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