<p>A reduction from 0,1 knapsack to subset-sum is described in Theorem 2 of the paper <a href="https://arxiv.org/abs/1208.4225" rel="nofollow noreferrer">"Reducing a Target Interval to a Few Exact Queries"</a>.  It proceeds in three steps.  First, reduce knapsack to a decision problem that tests whether there is a subset with weight at most b and value at least t.  This can be done by binary search over thresholds.  Second, reduce this decision problem to a small set of exact queries of the form "is there a subset with weight exactly b and value exactly t?"  This is a clever reduction that does not require enumerating all possible b's and t's.  Third, reduce this exact query to subset-sum by mapping each (weight,value) pair into the integer (weight*C + value) for sufficiently large C.</p>
Reduction of 0,1 knapsack to subset sum
<p>I know how to reduce subset sum to 0,1 knapsack. But is it possible to reduce knapsack to subset sum? How?</p>