【luogu P1113 杂务】 题解

题目链接：https://www.luogu.org/problemnew/show/P1113
菜

#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int maxn = 50000 + 10;
const int inf = 0x7fffffff;
int n, m, s, dis[maxn], w[maxn], du[maxn], ans;
bool vis[maxn];
queue<int> q;
struct edge{
	int from, to, next, len;
}e[maxn<<2];
int head[maxn], cnt;
void add(int u, int v, int w)
{
	e[++cnt].from = u;
	e[cnt].len = w;
	e[cnt].next = head[u];
	e[cnt].to = v;
	head[u] = cnt;
}
void SPFA(int s)
{
	while(!q.empty()) q.pop();
	for(int i = 1; i <= n; i++) dis[i] = inf, vis[i] = 0;
	q.push(s);
	dis[s] = w[s];
	vis[s] = 1;
	while(!q.empty())
	{
		int now = q.front(); q.pop();
		vis[now] = 0;
		for(int i = head[now]; i != -1; i = e[i].next)
		{
			if(dis[e[i].to] > dis[now] + e[i].len)
			{
				dis[e[i].to] = dis[now] + e[i].len;
				if(!vis[e[i].to])
				{
					q.push(e[i].to);
					vis[e[i].to] = 1;
				}
			}
		}
	}
}
int main()
{
	memset(head, -1, sizeof(head));
	scanf("%d",&n);
	for(int i = 1; i <= n; i++)
	{
		int uu, vv, ww;
		scanf("%d%d",&vv,&ww);
		w[vv] = -1*ww;
		while(scanf("%d",&uu) && uu != 0)
		{
			add(uu, vv, -1*ww);
			du[vv]++;
		}
	}
	//for(int i = 1; i <= n; i++) cout<<w[i]<<" ";
	for(int i = 1; i <= n; i++)
	{
		ans = inf;
		if(du[i] == 0) SPFA(i);
		for(int j = 1; j <= n; j++)
		{
			if(ans > dis[j])
			ans = dis[j];
		}
	}
	printf("%d",-ans);
	return 0;
}