제출 #670104

#제출 시각아이디문제언어결과실행 시간메모리
670104radal구슬과 끈 (APIO14_beads)C++17
0 / 100
3 ms4948 KiB
#include <bits/stdc++.h> #pragma GCC target("sse,sse2,avx2") #pragma GCC optimize("unroll-loops,O2") #define rep(i,l,r) for (int i = l; i < r; i++) #define repr(i,r,l) for (int i = r; i >= l; i--) #define X first #define Y second #define all(x) (x).begin() , (x).end() #define pb push_back #define endl '\n' #define debug(x) cerr << #x << " : " << x << endl; using namespace std; typedef long long ll; typedef pair<int,int> pll; constexpr int N = 2e5+10,mod = 1e9+7,maxm = 210; constexpr ll inf = 1e9+10; inline int mkay(int a,int b){ if (a+b >= mod) return a+b-mod; // if (a+b < 0) return a+b+mod; return a+b; } inline int poww(int a,int k){ if (k < 0) return 0; int z = 1; while (k){ if (k&1) z = 1ll*z*a%mod; a = 1ll*a*a%mod; k >>= 1; } return z; } vector<pll> adj[N]; int dp[N][2][2]; void dfs(int v,int p,int pw){ if ((int) adj[v].size() == 1){ dp[v][1][0] = dp[v][1][1] = dp[v][0][1] = -2*inf; dp[v][0][0] = 0; return; } vector<int> ve; int s = 0; for (auto [u,w] : adj[v]){ if (u == p) continue; dfs(u,v,w); int val = max({dp[u][0][0],dp[u][0][1],dp[u][1][0],dp[u][1][1]}); s += val; ve.pb(max(dp[u][1][0],dp[u][0][0])-val+w); } sort(all(ve)); int sz = ve.size(); dp[v][0][0] = s; dp[v][0][1] = -2*inf; dp[v][1][1] = s+ve.back()+pw; if (sz > 1) dp[v][1][0] = s+ve[sz-1]+ve[sz-2]; else dp[v][1][0] = -2*inf; } int main(){ ios :: sync_with_stdio(0); cin.tie(0); int n; cin >> n; rep(i,1,n){ int u,v,w; cin >> u >> v >> w; adj[u].pb({v,w}); adj[v].pb({u,w}); } if (n <= 2){ cout << 0 << endl; return 0; } int r = -1; rep(i,1,n+1) if ((int) adj[i].size() > 1){ r = i; break; } dfs(r,0,-2*inf); cout << max(dp[r][1][0],dp[r][0][0]); }
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