Submission #261381

#	Time	Username	Problem	Language	Result	Execution time	Memory
261381		Mercenary	Beads and wires (APIO14_beads)	C++14	100 / 100	371 ms	30724 KiB

beads

#include<bits/stdc++.h>
#define taskname "A"
#define pb push_back
#define mp make_pair
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;

typedef pair<int,int> ii;
const int maxn = 2e5 + 5;
int n;
ll dp[maxn][2][2];

vector<ii> adj[maxn];

void dfs(int u , int par , int parcost){
    ll sum = 0;
    for(auto & c : adj[u]){
        if(c.first == par)continue;
        dfs(c.first , u , c.second);
        sum += dp[c.first][0][0];
    }
    dp[u][0][0] = dp[u][0][1] = dp[u][1][0] = dp[u][1][1] = sum;
    {
        vector<ll> val;
        ll tmp1 = 0;
        for(auto & c : adj[u]){
            if(c.first == par)continue;
            tmp1 = max(tmp1 , dp[c.first][0][1] - dp[c.first][0][0]);
            val.pb(dp[c.first][1][0] + c.second - dp[c.first][0][0]);
        }
        if(val.size() >= 2){
            sort(val.begin(),val.end(),greater<ll>());
            for(auto & c : adj[u]){
                if(c.first == par)continue;
                if(val[0] == dp[c.first][1][0] + c.second - dp[c.first][0][0]){
                    dp[u][1][1] = max(dp[u][1][1] , sum + val[1] + max(dp[c.first][1][0],dp[c.first][1][1]) + c.second - dp[c.first][0][0]);
                }else{
                    dp[u][1][1] = max(dp[u][1][1] , sum + val[0] + max(dp[c.first][1][0],dp[c.first][1][1]) + c.second - dp[c.first][0][0]);
                }
            }
        }
        dp[u][1][1] = max(dp[u][1][1] , sum + tmp1);
    }
    {
        vector<ll> val;
        for(auto & c : adj[u]){
            if(c.first == par)continue;
            val.pb(dp[c.first][1][0] + c.second - dp[c.first][0][0]);
        }
        sort(val.begin(),val.end(),greater<ll>());
        if(val.size() >= 1)dp[u][0][0] = max(dp[u][0][0] , dp[u][0][0] + parcost + val[0]);
        else dp[u][0][0] = -1e9;
        dp[u][0][0] = max(dp[u][0][0] , dp[u][1][0]);
    }
    {
        vector<ll> val;
        for(auto & c : adj[u]){
            if(c.first == par)continue;
            val.pb(max(dp[c.first][1][1],dp[c.first][1][0]) + c.second - dp[c.first][0][0]);
        }
        sort(val.begin(),val.end(),greater<ll>());
        if(val.size() >= 1)dp[u][0][1] = max(dp[u][0][1] , dp[u][0][1] + parcost + val[0]);
        else dp[u][0][1] = -1e9;
        dp[u][0][1] = max(dp[u][0][1] , dp[u][1][1]);
        dp[u][0][1] = max(dp[u][0][1] , dp[u][0][0]);
    }
//    cout << u << " " << dp[u][0][0] << " " << dp[u][0][1] << " " << dp[u][1][0] << " " << dp[u][1][1] << endl;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    if(fopen(taskname".inp", "r")) {
        freopen(taskname".inp", "r", stdin);
        freopen(taskname".out", "w", stdout);
    }
    cin >> n;
    for(int i = 1 ; i < n ; ++i){
        int u , v , c;cin >> u >> v >> c;
        adj[u].pb(mp(v,c));adj[v].pb(mp(u , c));
    }
    dfs(1 , 0 , 0);
    cout << max(dp[1][1][0] , dp[1][1][1]);
}

Compilation message (stderr)

beads.cpp: In function 'int main()':
beads.cpp:80:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen(taskname".inp", "r", stdin);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
beads.cpp:81:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen(taskname".out", "w", stdout);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 13 / 13
• Subtask 2: 15 / 15
• Subtask 3: 29 / 29
• Subtask 4: 43 / 43