https://leetcode.cn/problems/minimum-cost-to-reach-destination-in-time/solution/gui-ding-shi-jian-nei-dao-da-zhong-dian-n3ews/ 也许最短路的本质是dp https://leetcode.cn/problems/cheapest-flights-within-k-stops/solution/k-zhan-zhong-zhuan-nei-zui-bian-yi-de-ha-abzi/ 限制时间/次数时，贝尔曼福德更好想
tomiz
