update

src/P1352/P1352.cpp

@@ -1,16 +1,27 @@
+#include <algorithm>
 #include <cstdint>
 #include <iostream>
+#include <istream>
+#include <stdexcept>
 #include <vector>
 
 using std::cin, std::cout;
 using ll = int64_t;
 const ll max_n = 6e3+5;
-ll n, r[max_n];
+ll n, r[max_n], dp[max_n][2], ind[max_n];
 std::vector<ll> sons[max_n];
 
-
+void dfs(const ll &now){
+    dp[now][1]=r[now];
+    for(const ll &next: sons[now]){
+        dfs(next);
+        dp[now][1] += dp[next][0];
+        dp[now][0] += std::max(dp[next][0], dp[next][1]);
+    }
+}
 
 int main(){
+    std::iostream::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
     cin>>n;
     for(ll i{1};i<=n;i++){
         cin>>r[i];
@@ -19,5 +30,16 @@ int main(){
         ll l, k;
         cin>>l>>k;
         sons[k].emplace_back(l);
+        ind[l]++;
+    }
+    const ll mst = [&]()->ll{
+        for(ll i{1}; i<=n; i++){
+            if(ind[i]==0){
+                return i;
             }
         }
+        throw std::runtime_error("unreachable");
+    }();
+    dfs(mst);
+    cout<<std::max(dp[mst][0], dp[mst][1])<<'\n';
+}