题目传送门

就只A了3个点

dalao求调

#include <bits/stdc++.h>
#define int long long
#define DB double

using namespace std;

const int N = 1e6 + 10, INF = 1e15;
int n, root, ans;
int val[N], dp[N][2], fa[N];
bool vis[N];
vector <int> v[N];

void dfs(int x)
{
	dp[x][0] = 0;
	dp[x][1] = val[x];
	vis[x] = true;
	
	for(auto y : v[x])
	{
		if(y != root) 
		{
			dfs(y);
			dp[x][0] += max(dp[y][0], dp[y][1]);
			dp[x][1] += dp[y][0];
		}
		else dp[y][1] = -INF;
	}
}

void findcircle(int x)
{
	vis[x] = true;
	root = x;
	while(vis[root] == false)
		root = fa[root], vis[root] = true;
	
	dfs(root);
	int t = max(dp[root][0], dp[root][1]);
	root = fa[root];
	dfs(root);
	ans += max({t, dp[root][0], dp[root][1]});
	
	return ;
}

int read()
{
    char a = getchar();
    while(a < '0' || a > '9')
        a = getchar();
    
    int t = 0;
    while(a <= '9' && a >= '0')
    {
        t = (t << 1) + (t << 3) + a - '0';
        a = getchar();
    }
    return t;
}

signed main()
{
	n = read();
//	scanf("%lld", &n);
	int x;
	for(int i = 1; i <= n; i ++ )
	{
		val[i] = read(), x = read();
//		scanf("%lld%lld", &val[i], &x);
		v[x].push_back(i);
		fa[i] = x;
	}
	
	for(int i = 1; i <= n; i ++ )
	{
		if(!vis[i])
			findcircle(i);
	}
	
	printf("%lld", ans);
	
	return 0;
}