✅ 活动人数 十四届蓝桥杯青少年组省赛

counting-people/main.cc

@@ -0,0 +1,46 @@
+#include <cstring>
+#include <iostream>
+#include <vector>
+using namespace std;
+
+const int MAXN = 1e5 + 5;
+
+vector<int> tree[MAXN];
+int amount[MAXN];
+int mem[MAXN][2];
+int N, Rt;
+
+int dfs(int node, int flag) {
+  if (mem[node][flag] > -1) {
+    return mem[node][flag];
+  }
+
+  mem[node][0] = 0;
+  mem[node][1] = amount[node];
+
+  for (int i = 0; i < tree[node].size(); i++) {
+    int leaf = tree[node][i];
+    mem[node][0] += max(dfs(leaf, 0), dfs(leaf, 1));
+    mem[node][1] += dfs(leaf, 0);
+  }
+
+  return mem[node][flag];
+}
+
+int main() {
+  // Init
+  cin >> N;
+  memset(mem, -1, sizeof mem);
+  for (int i = 0; i < N; i++) {
+    int depends, idx, c;
+    cin >> depends >> idx >> c;
+    amount[idx] = c;
+    if (depends == 0) {
+      Rt = idx;
+    } else {
+      tree[depends].push_back(idx);
+    }
+  }
+  // Calculating!
+  printf("%d", max(dfs(Rt, 1), dfs(Rt, 0)));
+}

counting-people/main.in

@@ -0,0 +1,7 @@
+6
+0 1 2
+1 2 4
+1 3 3
+2 4 3
+3 5 2
+3 6 4