Submission #438488

#	Time	Username	Problem	Language	Result	Execution time	Memory
438488		2548631	Beads and wires (APIO14_beads)	C++17	100 / 100	274 ms	21436 KiB

beads

#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef complex<ld> cp;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vii;
typedef vector<cp> vcp;
typedef vector<ld> vld;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef vector<vii> vvii;
 
#define fastIO ios_base::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL)
#define forw(i,l,r) for( int i = (l) ; i < (r) ; i++ )
#define forb(i,r,l) for( int i = (r) ; i >= (l) ; i-- )
#define log2i(x) (64 - __builtin_clzll(1ll*(x)) - 1)
#define numBit(x) (__builtin_popcountll(1ll*(x)))
#define getBit(x,i) (x>>i&1)
#define Pi acos(-1.0l)
#define sz(x) (int)x.size()
#define mt make_tuple
#define mp make_pair
#define fi first
#define se second
#define pb push_back
#define pf push_front
#define pob pop_back
#define pof pop_front
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define debug(x) cerr << #x << " = " << x << '\n';
 
const int N = 2e5+7;
const int inf = 2e9+7;
int n,ans=0;
int dp[N][2];
vii edge[N];
 
void solve(int u, int par=-1) {
    int tot=0;
    for(auto v:edge[u]) if(v.fi!=par) {
        solve(v.fi,u);
        tot+=max(dp[v.fi][0],dp[v.fi][1]+v.se);
    }
    dp[u][0]=tot; dp[u][1]=-inf;
    for(auto v:edge[u]) if(v.fi!=par) {
        int sum=v.se+dp[v.fi][0]-max(dp[v.fi][0],dp[v.fi][1]+v.se);
        dp[u][1]=max(dp[u][1],sum+tot);
    }
}
 
void reroot(int u, int par=-1) {
    ans=max(ans,dp[u][0]);
    pii tmp={-inf,-inf};
    for(auto v:edge[u]) {
        int sum=v.se+dp[v.fi][0]-max(dp[v.fi][0],dp[v.fi][1]+v.se);
        if(tmp.fi<sum) tmp.se=tmp.fi, tmp.fi=sum;
        else if(tmp.fi==sum) tmp.se=sum;
        else tmp.se=max(tmp.se,sum);
    }
    for(auto v:edge[u]) if(v.fi!=par) {
        bool ma=(v.se+dp[v.fi][0]-max(dp[v.fi][0],dp[v.fi][1]+v.se)==tmp.fi);
        int tmp_dp=dp[v.fi][1];
        dp[u][1]-=max(dp[v.fi][0],dp[v.fi][1]+v.se);
        if(ma) dp[u][1]+=tmp.se-tmp.fi;
        dp[u][0]-=max(dp[v.fi][0],dp[v.fi][1]+v.se);
        dp[v.fi][1]+=max(dp[u][0],dp[u][1]+v.se);
        dp[v.fi][1]=max(dp[v.fi][1],dp[v.fi][0]+v.se+dp[u][0]);
        dp[v.fi][0]+=max(dp[u][0],dp[u][1]+v.se);
        reroot(v.fi,u);
        dp[v.fi][0]-=max(dp[u][0],dp[u][1]+v.se);
        dp[v.fi][1]=tmp_dp;
        dp[u][0]+=max(dp[v.fi][0],dp[v.fi][1]+v.se);
        dp[u][1]+=max(dp[v.fi][0],dp[v.fi][1]+v.se);
        if(ma) dp[u][1]-=tmp.se-tmp.fi;
    }
}
 
int main() {
    fastIO;
#ifndef ONLINE_JUDGE
    //freopen("test.inp","r",stdin);
    //freopen("test.out","w",stdout);
#endif // ONLINE_JUDGE
 
    cin >> n;
    forw(i,1,n) {
        int u,v,w; cin >> u >> v >> w;
        u--, v--;
        edge[u].pb(mp(v,w));
        edge[v].pb(mp(u,w));
    }
    solve(0);
    reroot(0);
    cout << ans;
    return 0;
}

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