Bidirectional BFS
Expand from both S and E simultaneously; meet in the middle. LC 127 (Word Ladder), 433, 752.
Front frontier
Back frontier
Front visited
Back visited
Meeting point / path
Controls
Click cells to toggle walls.
Time: O(b^(d/2)) vs O(b^d) for normal BFS
Steps
0 stepsPress Run to trace the algorithm one step at a time.