第一题 govar dfs func(idx int, left int, count int)dfs = func(idx int, left int, count int) {if left <= 0 &amp;&amp; count == 0 {ans++return}if count == 0 &amp;&amp; left > 0 {return}if idx >= n {return}dfs(idx+1, left, count)dfs(idx+1, left-arr[idx], count-1)}