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164 | #include<bits/stdc++.h>
using namespace std;
typedef long long i64;
const int INF = 1e9;
const i64 INFL = 1e18;
const int MAXN = 1e5 + 3;
using edge = tuple<int, int, int>;
vector <edge> E[MAXN];
vector <edge> W;
vector <int> C;
edge F[MAXN];
bool V[MAXN];
int I[MAXN], o;
void dfs0(int u, int e){
V[u] = true;
I[u] = ++ o;
for(auto &[i, v, w] : E[u]) if(i != e){
if(V[v]){
if(I[v] < I[u]){
for(int p = u;p != v;){
auto &[j, f, x] = F[p];
C.push_back(p);
W.push_back({j, p, x});
p = f;
}
C.push_back(v);
W.push_back({i, v, w});
}
} else {
F[v] = {i, u, w};
dfs0(v, i);
}
}
}
namespace Problem2{
// ===== 删除环上第 i 条边，求直径 =====
i64 H[MAXN], A1[MAXN], B1[MAXN], A2[MAXN], B2[MAXN], A3[MAXN], B3[MAXN];
i64 L[MAXN];
i64 dis = 0;
void dfs1(int u, int e){
for(auto &[i, v, w] : E[u]) if(i != e){
if(!V[v]){
dfs1(v, i);
dis = max(dis, L[u] + w + L[v]);
L[u] = max(L[u], L[v] + w);
}
}
}
int main(){
int n;
cin >> n;
for(int i = 1;i <= n;++ i){
int u, v, w;
cin >> u >> v >> w;
E[u].push_back({i, v, w});
E[v].push_back({i, u, w});
}
dfs0(1, 0);
memset(V, 0, sizeof(V));
for(auto &u : C)
V[u] = true;
for(auto &u : C){
dfs1(u, 0);
}
int l = 0, r = C.size() - 1;
for(int i = l;i <= r;++ i){
int x = C[i];
if(i > 0)
H[i] = H[i - 1] + get<2>(W[i - 1]);
A1[i] = L[x] + H[i];
B1[i] = L[x] - H[i];
A2[i] = L[x] - H[i];
B2[i] = L[x] + H[i];
}
i64 h = H[r] + get<2>(W.back());
for(int i = l;i <= r;++ i)
A1[i] = max(i == l ? -INFL : A1[i - 1], L[C[i]] + H[i]),
A2[i] = max(i == l ? -INFL : A2[i - 1], L[C[i]] - H[i]);
for(int i = r;i >= l;-- i)
B1[i] = max(i == r ? -INFL : B1[i + 1], L[C[i]] - H[i]),
B2[i] = max(i == r ? -INFL : B2[i + 1], L[C[i]] + H[i]);
A3[l] = -INFL, B3[r] = -INFL;
for(int i = l + 1;i <= r;++ i){
int x = C[i];
i64 w = A2[i - 1] + L[x] + H[i];
A3[i] = max(A3[i - 1], w);
}
for(int i = r - 1;i >= l;-- i){
int x = C[i];
i64 w = B2[i + 1] + L[x] - H[i];
B3[i] = max(B3[i + 1], w);
}
i64 t = INFL;
for(int i = l;i < r;++ i){
i64 d = A1[i] + B1[i + 1] + h;
i64 g = A2[i] + B2[i + 1] + 0;
d = max({d, dis, A3[i], B3[i + 1]});
t = min(t, d);
}
t = min(t, max(A3[r], dis));
if(t % 2 == 0)
cout << t / 2 << ".0" << endl;
if(t % 2 == 1)
cout << t / 2 << ".5" << endl;
return 0;
}
}
namespace Problem3{
// ===== 求最大点权独立集 =====
int A[MAXN];
i64 X[MAXN], Y[MAXN];
i64 P[MAXN][2], Q[MAXN][2];
void dfs1(int u, int e){
for(auto &[i, v, w] : E[u]) if(i != e){
if(!V[v]){
dfs1(v, i);
Y[u] += max(X[v], Y[v]);
X[u] += Y[v];
}
}
X[u] += A[u];
}
int main(){
int n;
cin >> n;
for(int i = 1;i <= n;++ i){
cin >> A[i];
}
for(int i = 1;i <= n;++ i){
int u, v;
cin >> u >> v;
++ u, ++ v;
E[u].push_back({i, v, 0});
E[v].push_back({i, u, 0});
}
double p;
cin >> p;
dfs0(1, 0);
memset(V, 0, sizeof(V));
for(auto &u : C)
V[u] = true;
for(auto &u : C){
dfs1(u, 0);
}
int l = 0, r = C.size() - 1;
P[0][1] = X[C[0]];
P[0][0] = -INFL;
Q[0][0] = Y[C[0]];
Q[0][1] = -INFL;
for(int i = l + 1;i <= r;++ i){
int x = C[i];
P[i][1] = X[x] + P[i - 1][0];
P[i][0] = Y[x] + max(P[i - 1][0], P[i - 1][1]);
Q[i][1] = X[x] + Q[i - 1][0];
Q[i][0] = Y[x] + max(Q[i - 1][0], Q[i - 1][1]);
}
i64 ans = max({P[r][0], Q[r][0], Q[r][1]});
cout << fixed << setprecision(1) << ans * p << endl;
return 0;
}
}
int main(){
return Problem3 :: main();
}
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