标准的拓扑排序

#include <stdio.h>
#include <queue>
#include <vector>
#include <algorithm>
#define N 1020
using namespace std;

int n, m;
int indegree[N], a[N], b[N], books[N][N];
vector<int>e[N];
struct edge {
	int start;
	int temp;
};
queue<edge>q;
int bfs()
{
	int i, v, s, ans = 1;
	
	for(i=1; i<=n; i++)
		if (indegree[i] == 0)
			q.push(edge{ i, 1 });
	while (!q.empty())
	{
		edge u = q.front();
		q.pop();
		s = u.start;
		ans = max(ans, u.temp);
		for (i = 0; i < e[s].size(); i++)
		{
			v = e[s][i];
			indegree[v]--;
			if (indegree[v] == 0)
				q.push(edge{ v, u.temp + 1 });
		}
	}
	return ans;
}
int main()
{
	int i, j, k, l, len;
	scanf("%d%d", &n, &m);
	while (m--)
	{
		scanf("%d", &k);
		for (i = 0; i < k; i++)
			scanf("%d", &a[i]);
		l = 1;
		len = 0;
		for (j = a[0] + 1; j < a[k - 1]; j++)
		{
			if (j == a[l])
			{
				l++;
				continue;
			}
			b[len++] = j;
		}
		for (i = 0; i < k; i++)
		{
			for (j = 0; j < len; j++)
			{
				if (books[a[i]][b[j]])
					continue;
				e[a[i]].push_back(b[j]);
				indegree[b[j]]++;
				books[a[i]][b[j]] = 1;
			}
			
		}
	}
	printf("%d\n", bfs());
	return 0;
}