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5.5 Exercises

Basic Difficulty​

130. Surrounded Regions​

Start by filling from the outer edges, then consider the inner regions.

257. Binary Tree Paths​

Output all paths from the root to the leaves in a binary tree. What is the difference if backtracking is used?

Advanced Difficulty​

47. Permutations II​

A follow-up to the permutations problem. How to handle duplicate elements?

40. Combination Sum II​

A follow-up to the combination problem. How to handle duplicate elements?

37. Sudoku Solver​

A very classic Sudoku problem that can be solved using backtracking. In fact, there are many advanced search methods and pruning strategies, such as heuristic search, to improve speed for Sudoku-related problems.

310. Minimum Height Trees​

How can this problem be transformed into a search problem? Should depth-first search or breadth-first search be used?