Submission #797007

#	Time	Username	Problem	Language	Result	Execution time	Memory
797007		GrindMachine	Power Plant (JOI20_power)	C++17	100 / 100	350 ms	145244 KiB

power

// Om Namah Shivaya

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl

#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a, b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a, b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif

/*

read edi long time ago, dont exactly remember the approach in the edi

*/

const int MOD = 1e9 + 7;
const int N = 2e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

vector<ll> adj[N];
vector<ll> a(N);
array<ll,3> dp[N];
vector<ll> best(N);

array<ll,3> merge(array<ll,3> v1, array<ll,3> v2){
    array<ll,3> v3;
    v3.fill(0);

    rep(i,3){
        rep(j,3){
            ll j2 = min(i+(j>0),2);
            amax(v3[j2],v1[i]+v2[j]);
        }
    }

    return v3;
}

void dfs1(ll u, ll p){
    dp[u].fill(0);

    trav(v,adj[u]){
        if(v == p) conts;
        dfs1(v,u);
        dp[u] = merge(dp[u],dp[v]);
    }

    if(a[u]){
        best[u] = max(dp[u][1]+1,dp[u][2]-1);

        dp[u][1]--;
        dp[u][2]--;
        amax(dp[u][1],1ll);
        amax(dp[u][2],1ll);
    }
}

array<ll,3> from_up[N];

void dfs2(ll u, ll p){
    if(u == 1){
        from_up[u].fill(0);
    }

    auto here = from_up[u];
    trav(v,adj[u]){
        if(v == p) conts;
        here = merge(here,dp[v]);
    }

    if(a[u]){
        best[u] = max(here[1]+1,here[2]-1);
    }

    ll siz = sz(adj[u]);
    vector<array<ll,3>> pref(siz+5), suff(siz+5);
    
    rep1(i,siz){
        pref[i] = pref[i-1];
        ll v = adj[u][i-1];
        if(v == p) conts;
        pref[i] = merge(pref[i-1],dp[v]);
    }

    rev(i,siz,1){
        suff[i] = suff[i+1];
        ll v = adj[u][i-1];
        if(v == p) conts;
        suff[i] = merge(suff[i+1],dp[v]);
    }

    rep1(i,siz){
        ll v = adj[u][i-1];
        if(v == p) conts;
        
        auto curr = from_up[u];
        curr = merge(curr,pref[i-1]);
        curr = merge(curr,suff[i+1]);

        if(a[u]){
            curr[1]--;
            curr[2]--;
            amax(curr[1],1ll);
            amax(curr[2],1ll);
        }

        amax(curr[1],curr[2]);

        from_up[v] = curr;

        dfs2(v,u);
    }
}

void solve(int test_case)
{
    ll n; cin >> n;
    rep1(i,n-1){
        ll u,v; cin >> u >> v;
        adj[u].pb(v), adj[v].pb(u);
    }    

    rep1(i,n){
        char ch; cin >> ch;
        a[i] = ch-'0';
    }

    dfs1(1,-1);
    dfs2(1,-1);

    ll ans = 0;
    rep1(i,n) amax(ans,best[i]);

    cout << ans << endl;
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;

    rep1(i, t) {
        solve(i);
    }

    return 0;
}

• Subtask 1: 6 / 6
• Subtask 2: 41 / 41
• Subtask 3: 53 / 53