Introduction to Backtracking Pattern

You are given candidate numbers and a target. Find every combination that adds up to the target, where each candidate may be used any number of times.

candidates [2, 3, 6, 7]   target 7   gives [2, 2, 3] and [7]

The Subsets pattern would build every possible combination and then throw away the ones that miss the target. That is correct and wasteful. Once a partial combination has reached 8, no amount of adding will bring it back to 7, and yet the Subsets approach keeps extending it.