77. Combinations

{leetcode}/problems/combinations/[LeetCode - Combinations^]

Given two integers n and k, return all possible combinations of k numbers out of 1 … n.

Example:

Input: n = 4, k = 2
Output:
[
  [2,4],
  [3,4],
  [2,3],
  [1,2],
  [1,3],
  [1,4],
]

思路分析

要注意和 46. Permutations 的区别。

注意剪枝！

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一刷

link:{sourcedir}/_0077_Combinations.java[role=include]

二刷

link:{sourcedir}/_0077_Combinations_2.java[role=include]

尝试一下字典序组合解法。