Submission #434860

#	Time	Username	Problem	Language	Result	Execution time	Memory
434860		cpp219	Beads and wires (APIO14_beads)	C++14	0 / 100	3 ms	4940 KiB

beads

#pragma GCC optimization O2
#pragma GCC optimization "unroll-loop"
#pragma target ("avx2")

#include <bits/stdc++.h>
#define ll int
#define ld long double
#define fs first
#define sc second
using namespace std;
typedef pair<ll,ll> LL;
const ll N = 2e5 + 9;
const ll inf = 1e9 + 7;
vector<LL> g[N];
ll n,x,y,w,dp[N][2],ans,val[N];

void DFS(ll u,ll p){
    ll child = 0;
    for (auto i : g[u]) if (i.fs != p) DFS(i.fs,u),child++;
    dp[u][0] = dp[u][1] = 0;
    if (!child) dp[u][1] = -inf;
    for (auto i : g[u]){
        ll v = i.fs,cost = i.sc;
        if (v == p) continue;
        dp[u][0] += max(dp[v][1] + cost,dp[v][0]);
        val[v] = dp[v][0] + cost - max(dp[v][1] + cost,dp[v][0]);
    }
    for (auto i : g[u]){
        ll v = i.fs,cost = i.sc;
        if (v == p) continue;
        ll now = dp[u][0] - max(dp[v][1] + cost,dp[v][0]) + dp[v][0] + cost;
        dp[u][1] = max(dp[u][1],now);
    }
    if (child < 2) return;
    //cout<<val[5]; exit(0);
    multiset<ll> s;
    for (auto i : g[u]){
        ll v = i.fs,cost = i.sc;
        if (v == p) continue;
        s.insert(val[v]);
    }
    while(s.size() > 2) s.erase(s.begin());
    dp[u][0] += max(0,*s.begin() + *s.rbegin());
}
int main(){
    ios_base::sync_with_stdio(NULL); cin.tie(0); cout.tie(0);
    #define task "tst"
    if (fopen(task".INP","r")){
        freopen(task".INP","r",stdin);
        //freopen(task".OUT","w",stdout);
    }
    cin>>n;
    for (ll i = 1;i < n;i++){
        cin>>x>>y>>w;
        g[x].push_back({y,w}); g[y].push_back({x,w});
    }
    DFS(1,0);
    cout<<dp[1][0]; return 0;
    for (ll i = 1;i <= min(n,2000);i++){
        DFS(i,0);
        ans = max(ans,dp[i][0]); //cout<<dp[i][0]; return 0;
    }
    cout<<ans;
}

Compilation message (stderr)

beads.cpp:1: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    1 | #pragma GCC optimization O2
      | 
beads.cpp:2: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    2 | #pragma GCC optimization "unroll-loop"
      | 
beads.cpp:3: warning: ignoring '#pragma target ' [-Wunknown-pragmas]
    3 | #pragma target ("avx2")
      | 
beads.cpp: In function 'void DFS(int, int)':
beads.cpp:38:21: warning: unused variable 'cost' [-Wunused-variable]
   38 |         ll v = i.fs,cost = i.sc;
      |                     ^~~~
beads.cpp: In function 'int main()':
beads.cpp:49:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   49 |         freopen(task".INP","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 13
• Subtask 2: 0 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43