path-length of binary tree

例句：

1. 1. Thepath length from the city center to thebeach is about 5 kilometers.
   从市中心到海滩的路径长度大约是5公里。
2. 2.The path length of the mountain trail isquite steep.
   这条山间小径的路径长度相当陡峭。
3. 3. The path length measurement iscrucial for determining the optimal route.
   路径长度测量对于确定最佳路线至关重要。