https://www.rik-kisnah.ai/tags/combinatorics/Recent content in Combinatorics on Rik Kisnah - BlogHugoenTue, 10 Jun 2025 09:00:00 -0700https://www.rik-kisnah.ai/teach/coding/subsets/Tue, 10 Jun 2025 09:00:00 -0700https://www.rik-kisnah.ai/teach/coding/subsets/Every possible group you can make from a set of items, including the empty group. For each item, choose to take it or leave it. That choose-then-undo rhythm is backtracking, and it is behind every ‘all combinations’ question.https://www.rik-kisnah.ai/teach/coding/unique-paths/Tue, 08 Mar 2022 09:00:00 -0800https://www.rik-kisnah.ai/teach/coding/unique-paths/A robot in the top-left corner of a grid can only move right or down. How many ways to reach the bottom-right? Every cell is the sum of the cell above and the cell to its left. Fill the grid once.