Submission #401454

#	Time	Username	Problem	Language	Result	Execution time	Memory
401454		egekabas	The Xana coup (BOI21_xanadu)	C++14	100 / 100	124 ms	28220 KiB

xanadu

#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pull;
typedef pair<ll, ll> pii;
typedef pair<ld, ld> pld;
ll n;
vector<ll> g[100009];
ll st[100009];
ll dp[100009][2][2];
ll sf(pii a, pii b){
    return (a.ss-a.ff) < (b.ss-b.ff);
}
void dfs(ll v, ll prt){
    for(auto u : g[v])
        if(u != prt)
            dfs(u, v);
    for(ll use = 0; use < 2; ++use)
        for(ll res = 0; res < 2; ++res){
            ll curst = (st[v]^use);
            ll curv = use;
            vector<pii> vec;
            for(auto u : g[v])
                if(u != prt)
                    vec.pb({dp[u][0][use], dp[u][1][use]});
            sort(all(vec), sf);
            if(vec.empty()){
                if(curst == res)
                    dp[v][use][res] = curv;
                else
                    dp[v][use][res] = 1e9;
                continue;
            }
            ll idx = 0;
            if(curst != res){
                curv += vec[idx].ss;
                curst ^= 1;
                ++idx;
            }
            for(; idx < vec.size(); ++idx){
                if(idx != vec.size()-1 && vec[idx].ss+vec[idx+1].ss<vec[idx].ff+vec[idx+1].ff){
                    curv += vec[idx].ss+vec[idx+1].ss;
                    idx++;
                }
                else
                    curv += vec[idx].ff;
                
            }
            dp[v][use][res] = min(curv, (ll)1e9);
        }
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);

    cin >> n;
    for(ll i = 0; i < n-1; ++i){
        ll x, y;
        cin >> x >> y;
        g[x].pb(y);
        g[y].pb(x);
    }
    for(ll i = 1; i <= n; ++i)
        cin >> st[i];
    dfs(1, 0);
    if(min(dp[1][0][0], dp[1][1][0]) == 1e9)
        cout << "impossible\n";
    else
        cout << min(dp[1][0][0], dp[1][1][0]) << '\n';
}

Compilation message (stderr)

xanadu.cpp: In function 'void dfs(ll, ll)':
xanadu.cpp:48:23: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   48 |             for(; idx < vec.size(); ++idx){
      |                   ~~~~^~~~~~~~~~~~
xanadu.cpp:49:24: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   49 |                 if(idx != vec.size()-1 && vec[idx].ss+vec[idx+1].ss<vec[idx].ff+vec[idx+1].ff){
      |                    ~~~~^~~~~~~~~~~~~~~

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