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Prompt: Given an m x n grid, each cell contains a “X” or “O”. Can you capture all the “O” that are surrounded by “X”. To capture the surrounded “O”s, we need to turn them into “X”. [Read More]

Idea: The idea of dynamic programming(DP) is breaking down a large, complex problem into smaller, simple problems. [Read More]

Prompt: Given an m x n grid, how many unique paths are there with the start of the path being the top left corner and the end of the path being the bottom right corner? [Read More]

Idea: This pattern is indicated by a multi-day runner and into a steep dip. Then, you can buy at the potential bottom of the dip in order to profit the bounce. Or you can short before the dip. [Read More]

Prompt: Given a binary tree and two nodes from the tree, find the lowest common ancestor, LCA. [Read More]