Submission #867079

#	Time	Username	Problem	Language	Result	Execution time	Memory
867079		HossamHero7	The Xana coup (BOI21_xanadu)	C++14	55 / 100	71 ms	25024 KiB

xanadu

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define endl '\n'
vector<vector<int>> adj;
vector<int> on;
const int N = 1e5+5;
ll dp[N][3][2];
ll solve(int node,int par,int pressed,bool color){
    ll &ret = dp[node][pressed][color];
    if(~ret) return ret;
    ret = 1e9;
    if(pressed != 1){
        int sz = adj[node].size();
        if(node) sz --;
        for(int mask=0;mask<(1<<sz);mask++){
            bool changed = __builtin_popcount(mask) & 1;
            if((color^changed)) continue;
            ll c = 0;
            int idx = 0;
            for(auto ch : adj[node]){
                if(ch == par) continue;
                if(((mask>>idx)&1)) c += solve(ch,node,1,on[ch]^1) + 1;
                else c += solve(ch,node,0,on[ch]);
                idx ++;
            }
            ret = min(ret,c);
        }
    }
    if(pressed != 0){
        int sz = adj[node].size();
        if(node) sz --;
        for(int mask=0;mask<(1<<sz);mask++){
            bool changed = __builtin_popcount(mask) & 1;
            if(pressed == 1 && (color^changed)) continue;
            if(pressed == 2 && !((color^changed))) continue;
            ll c = 0;
            int idx = 0;
            for(auto ch : adj[node]){
                if(ch == par) continue;
                if(((mask>>idx)&1)) c += solve(ch,node,1,on[ch]) + 1;
                else c += solve(ch,node,0,on[ch]^1);
                idx ++;
            }
            if(pressed == 2) c ++;
            ret = min(ret,c);
        }
    }
    return ret;
}
void solve(){
    int n;
    cin>>n;
    adj.resize(n);
    for(int i=0;i<n-1;i++){
        int a,b;
        cin>>a>>b;
        a -- , b --;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    on.resize(n);
    for(int i=0;i<n;i++){
        int x;cin>>x;
        if(x) on[i] = 1;
    }
    memset(dp,-1,sizeof(dp));
    ll ans = solve(0,n,2,on[0]);
    if(ans >= 1e9) cout<<"impossible"<<endl;
    else cout<<ans<<endl;
}
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);      cout.tie(0);
    int t=1;
    //cin>>t;
    while(t--){
        solve();
    }
    return 0;
}

• Subtask 1: 5 / 5
• Subtask 2: 0 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 0 / 30