updating DIRECTORY.md

Author: github-actions

DIRECTORY.md

@@ -317,6 +317,7 @@
   * [Longest Sub Array](dynamic_programming/longest_sub_array.py)
   * [Matrix Chain Order](dynamic_programming/matrix_chain_order.py)
   * [Max Non Adjacent Sum](dynamic_programming/max_non_adjacent_sum.py)
+  * [Max Product Subarray](dynamic_programming/max_product_subarray.py)
   * [Max Sub Array](dynamic_programming/max_sub_array.py)
   * [Max Sum Contiguous Subsequence](dynamic_programming/max_sum_contiguous_subsequence.py)
   * [Min Distance Up Bottom](dynamic_programming/min_distance_up_bottom.py)