303. Combination Sum

Given an array of distinct integers candidates and a target integer target, return a list of all unique combinations of candidates where the chosen numbers sum to target. You may return the combinations in any order.

The same number may be chosen from candidates an unlimited number of times. Two combinations are unique if the frequency of at least one of the chosen numbers is different.

Find all combinations that sum to target, where each candidate can be reused. This is a classic backtracking problem with the key twist that elements can be repeated.

Requirements

1. Basic Functionality

• Find all unique combinations summing to target
• Each candidate can be used unlimited times
• No duplicate combinations in the result

Example Usage

combinationSum([2, 3, 6, 7], 7);
// [[2, 2, 3], [7]]

combinationSum([2, 3, 5], 8);
// [[2, 2, 2, 2], [2, 3, 3], [3, 5]]

Real-World Context

• Coin change variants: Finding all ways to make change
• Resource allocation: All ways to distribute budget across categories
• Recipe combinations: Finding ingredient combinations that meet nutritional targets