有关于图的最短路径算法，常用的Dijkstra和SPFA算法或可采用堆优化或可采用A*算法加速实现时间复杂度的大幅降低。但是本题中图的边长均为1，使用BFS的时间复杂度较Dijkstra和SPFA有更为明显的降低，尽管看上去BFS更为简单-Figure about the shortest path algorithm, commonly used Dijkstra algorithm and SPFA or heap can be used to optimize or A* algorithm to accelerate dramatically reduce the time complexity. However, this problem in the long side of the figure is 1, using BFS time complexity compared with Dijkstra and SPFA have a more significant reduction, even though it looked easier to BFS