new file: P1453.cpp

P1453.cpp

@@ -0,0 +1,49 @@
+#include <bits/stdc++.h>
+#define int long long
+using namespace std;
+int n;
+int p[100005];
+vector<int> fri[100005];
+long double k;
+int bc[100005];
+int find(int now) {
+    if(bc[now] == now) return now;
+    return bc[now] = find(bc[now]);
+}
+int dps[100005][2], dpt[100005][2];
+void dfs(int now, bool s, int from) {
+    if(s) dps[now][1] = p[now];
+    else dpt[now][1] = p[now];
+    if(s && now == T) dps[now][1] = LLONG_MIN;
+    else if(!s && now == S) dpt[now][1] = LLONG_MIN;
+    for(int i:fri[now]) {
+        if(i == from) continue;
+        dfs(i, s, now);
+        if(s) dps[now][1] += dps[i][0], dps[now][0] += max(dps[i][0], dps[i][1]);
+        else dpt[now][1] += dpt[i][0], dpt[now][0] += max(dpt[i][0], dpt[i][1]);
+    }
+}
+signed main() {
+    int S, T;
+    scanf("%lld", &n);
+    for(int i = 0; i < n; ++i) {
+        scanf("%lld", &p[i]);
+        bc[i] = i;
+    }
+    for(int i = 0, u, v; i < n; ++i) {
+        scanf("%lld%lld", &u, &v);
+        if(find(u) == find(v)) {
+            S = u, T = v;
+        } else {
+            fri[u].push_back(v);
+            fri[v].push_back(u);
+            bc[find(u)] = find(v);
+        }
+    }
+    scanf("%llf", &k);
+    dfs(S, 1, -1);
+    dfs(T, 0, -1);
+    int ans = max(max(dps[S][0], dps[S][1]), max(dpt[T][1], dpt[T][0]));
+    printf("%.1llf\n", ans * k);
+    return 0;
+}