Unique Paths — interactive algorithm visualization
Medium · Dynamic Programming · time O(m·n) · space O(m·n)
Fill a DP table where each cell is the sum of the cell above and to the left. The classic 2D DP recurrence.
Example input: m = 3, n = 3
Step through a verified execution trace - every step shows the real state, the invariant that keeps the algorithm correct, and asks you to predict what happens next.