Combination Sum III
描述
Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.
Ensure that numbers within the set are sorted in ascending order.
Example 1:
Input: k=3, n=7
Output: [[1,2,4]]
Example 2:
Input: k=3, n=9
Output: [[1,2,6], [1,3,5], [2,3,4]]
分析
这是一个多阶段问题，目标是求所有解，显然用深搜+剪枝，即回溯法。