> For the complete documentation index, see [llms.txt](https://liuzhenglaichn.gitbook.io/algorithm/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://liuzhenglaichn.gitbook.io/algorithm/graph/bi-directional-breadth-first-search.md).

# Bi Directional Breadth First Search

## Problems

* [127. Word Ladder (Hard)](https://leetcode.com/problems/word-ladder/)