洛谷 P1352 没有上司的舞会

题目链接：没有上司的舞会

思路

题解

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1e5 + 10;

int dp[N][2], happy[N], subordinate[N], cnt, head[N], nex[N], edge[N];
// 链式向前星存储边
void add(int x, int y) {
  nex[++cnt] = head[x];
  head[x] = cnt;
  edge[cnt] = y;
}

// 树形dp
void dfs(int x) {
	dp[x][0] = 0;
	dp[x][1] = happy[x];
	for (int i = head[x]; i; i = nex[i]) {
		int to = edge[i];
		dfs(to);
		dp[to][1] += dp[to][0];
		dp[to][0] += max(dp[to][0], dp[to][1]);
	}
}

int main() {
  int n, l, k;

  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> happy[i];
  }
  for (int i = 1; i < n; i++) {
    cin >> l >> k;
    add(k, l);
    subordinate[l] = true;
  }

  int root;
  for (int i = 1; i <= n; i++) {
    if (subordinate[i] == false) {
      root = i;
      break;
    }
  }

  dfs(root);
  cout << max(dp[root][0], dp[root][1]);

	return 0;
}