Submission #1114144

#	Time	Username	Problem	Language	Result	Execution time	Memory
1114144		ljtunas	The Xana coup (BOI21_xanadu)	C++14	100 / 100	62 ms	38472 KiB

xanadu

// author : anhtun_hi , nqg
#include <bits/stdc++.h>
#define ll long long
#define ii pair<ll, ll>
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define reset(h, v)    memset(h, v, sizeof h)
#define Forv(i, a)     for(auto& i : a)
#define For(i, a, b)   for(int i = a; i <= b; ++i)
#define Ford(i, a, b)  for(int i = a; i >= b; --i)
#define c_bit(i)     __builtin_popcountll(i)
#define Bit(mask, i)    ((mask >> i) & 1LL)
#define onbit(mask, i)  ((mask) bitor (1LL << i))
#define offbit(mask, i) ((mask) &~ (1LL << i))
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
using namespace std;
namespace std {
    template <typename T, int D>
    struct _vector : public vector <_vector <T, D - 1>> {
        static_assert(D >= 1, "Dimension must be positive!");
        template <typename... Args>
        _vector(int n = 0, Args... args) : vector <_vector <T, D - 1>> (n, _vector <T, D - 1> (args...)) {}
    };
    template <typename T> struct _vector <T, 1> : public vector <T> {
        _vector(int n = 0, const T& val = T()) : vector <T> (n, val) {}
    };
    template <class A, class B> bool minimize(A &a, B b){return a > b ? a = b, true : false;}
    template <class A, class B> bool maximize(A &a, B b){return a < b ? a = b, true : false;}
}
const int dx[] = {0, 0, +1, -1}, dy[] = {-1, +1, 0, 0}, LOG = 20, base = 311, inf = 1e9 + 5;
const int MAXN = 1e6 + 5;
const  ll  mod = 1e9 + 7;
const  ll   oo = 1e13;

//#define int long long

int n, a[MAXN];
vector<int> g[MAXN];
ll dp[MAXN][2][2];

void dfs(int u, int par){
    dp[u][a[u]][0]=0;
    dp[u][a[u]][1]=0;
    Forv(v, g[u]) if(v ^ par){
        dfs(v, u);
        ll dpu10=dp[u][1][0];
        ll dpu11=dp[u][1][1];
        ll dpu00=dp[u][0][0];
        ll dpu01=dp[u][0][1];
        dp[u][0][0]=min(dp[u][0][0]+dp[v][0][0], dpu10+dp[v][1][1]+1);
        dp[u][1][0]=min(dp[u][1][0]+dp[v][0][0], dpu00+dp[v][1][1]+1);
        dp[u][0][1]=min(dp[u][0][1]+dp[v][1][0], dpu11+dp[v][0][1]+1);
        dp[u][1][1]=min(dp[u][1][1]+dp[v][1][0], dpu01+dp[v][0][1]+1);
    }
}

void Solve() {
    cin >> n;
    For(i, 1, n - 1){
        int u, v; cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    For(i, 1, n) cin >> a[i];
    For(i,0,n)For(j,0,1)For(k,0,1)dp[i][j][k]=oo;
    dfs(1, 0);
    if (min(dp[1][0][0],dp[1][1][1]+1) < oo)cout<<min(dp[1][0][0],dp[1][1][1]+1)<<'\n';
    else cout <<"impossible";
}

signed main() {
    cin.tie(0) -> sync_with_stdio(0);
    if(fopen("BOI21_xanadu.inp", "r")) {
        freopen("BOI21_xanadu.inp", "r", stdin);
        freopen("BOI21_xanadu.out", "w", stdout);
    }

    int t = 1;
//    cin >> t;
    while(t --) Solve();

    return 0;
}

Compilation message (stderr)

xanadu.cpp: In function 'int main()':
xanadu.cpp:75:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   75 |         freopen("BOI21_xanadu.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
xanadu.cpp:76:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   76 |         freopen("BOI21_xanadu.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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