Section 1Understand Problem
Section 01
Understand the problem
Restate the problem precisely. Interviewers reward candidates who pause, define the contract, and name the guarantees before coding.
Problem statement
Find all valid combinations of k numbers that sum up to n such that the following conditions are true: only numbers 1 through 9 are used, and each number is used at most once. Return a list of all possible valid combinations. The list must not contain the same combination twice, and the combinations may be returned in any order.
Example
k = 3, n = 7 → [[1,2,4]]
Constraints
2 ≤ k ≤ 9 · 1 ≤ n ≤ 60
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