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Explore all possibilities by building and abandoning partial solutions
Given a collection of distinct integers, generate all possible permutations.
Given two integers n and k, generate all combinations of k numbers chosen from the range [1, n].
Given an array of unique integers, return all possible subsets (the power set).
Place n queens on an n x n chessboard such that no two queens attack each other.
Determine if a 9x9 Sudoku board is valid. A valid board has:
Given an m x n grid of characters and a target word, determine if the word exists in the grid.
Given a directed acyclic graph (DAG) with n nodes numbered 0 to n-1, find all paths from node 0 (source) to node n-1 (target).
Master the fundamental pattern. Each problem teaches you when and how to apply this technique.