<pre class="shiki github-dark shaku"><code>type Subtract&lt;A extends number, B extends number&gt; = chop&lt;totalOfFirst&lt;A&gt;,B&gt;type totalOfFirst&lt;A extends number,aArr extends any[]=[]&gt; = aArr['length'] extends A?aArr:totalOfFirst&lt;A,[...aArr,1]&gt;type chop&lt;T extends any[],B extends number,acc extends any[]=[]&gt;=acc['length'] extends B?T['length']:T extends [infer first,...infer rest]?chop&lt;rest,B,[...acc,1]&gt;:never</code></pre>

This is my accepted solution

Similar to 38. implement Add<A, B>, please implement Subtract<A, B>. 1. only need to consider positive integers 2. B is guaranteed to be smaller or eq…