Cheat Sheet

2-D DP Cheat Sheet

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What is 2-D DP?

Tackle grid and matrix problems with two-dimensional DP.

Trigger Words

When you see these in a problem, think 2-D DP:

unique paths 2d-dp longest common subsequence best time to buy and sell stock with cooldown coin change ii target sum interleaving string edit distance burst balloons

Template Code

def uniquePaths(m: int, n: int) -> int:
    # Space-optimized 1D DP
    dp = [1] * n
    
    for i in range(1, m):
        for j in range(1, n):
            dp[j] += dp[j - 1]
    
    return dp[n - 1]

Complexity

Typical Time	`O(m × n)`
Typical Space	`O(n)`

Common Variations

Basic 2-D DP
2-D DP with constraints
Optimized 2-D DP

Practice Problems

Unique Paths medium Longest Common Subsequence medium Best Time to Buy and Sell Stock with Cooldown medium Coin Change II medium Target Sum medium

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Practice 2-D DP

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