new file: P2607.cpp

P2607.cpp

@@ -0,0 +1,49 @@
+#include <bits/stdc++.h>
+#define int long long
+using namespace std;
+int n;
+int p[1000005];
+vector<int> fri[1000005];
+int bc[1000005];
+vector<pair<int, int>> ST;
+int find(int now) {
+    if(bc[now] == now) return now;
+    return bc[now] = find(bc[now]);
+}
+int dps[1000005][2], dpt[1000005][2];
+void dfs(int now, bool s, int from, int st) {
+    if(s) dps[now][1] = p[now];
+    else dpt[now][1] = p[now];
+    if(s && now == st) dps[now][1] = LLONG_MIN;
+    else if(!s && now == st) dpt[now][1] = LLONG_MIN;
+    for(int i:fri[now]) {
+        if(i == from) continue;
+        dfs(i, s, now, st);
+        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() {
+    scanf("%lld", &n);
+    for(int i = 1; i <= n; ++i) {
+        bc[i] = i;
+    }
+    for(int i = 1, v; i <= n; ++i) {
+        scanf("%lld%lld", &p[i], &v);
+        if(find(i) == find(v)) {
+            ST.push_back({i, v});
+        } else {
+            fri[i].push_back(v);
+            fri[v].push_back(i);
+            bc[find(i)] = find(v);
+        }
+    }
+    int ans = 0;
+    for(auto [s, t]:ST){
+        dfs(s, 1, -1, s);
+        dfs(t, 0, -1, t);
+        ans += max(max(dps[s][0], dps[s][1]), max(dpt[t][1], dpt[t][0]));
+    }
+    printf("%lld\n", ans);
+    return 0;
+}