2-D Dynamic Programming problems

The same idea as 1-D DP, tracked across two dimensions at once.

1. Unique Paths (Medium)
2. Longest Common Subsequence (Medium)
3. Best Time to Buy and Sell Stock with Cooldown (Medium)
4. Coin Change II (Medium)
5. Target Sum (Medium)
6. Interleaving String (Medium)
7. Longest Increasing Path in a Matrix (Hard)
8. Distinct Subsequences (Hard)
9. Edit Distance (Hard)
10. Burst Balloons (Hard)
11. Regular Expression Matching (Hard)