title: difference between k - 1 and --k here, really don't understand
body: <pre><code>class Solution {
      public List&lt;List&lt;Integer&gt;&gt; combine(int n, int k) {
          List&lt;List&lt;Integer&gt;&gt; res = new ArrayList&lt;&gt;();
          if (n == 0) {
              return res;
          }
          List&lt;Integer&gt; cur = new ArrayList&lt;&gt;();
          helper(res, cur, n, k, 1);
          return res;
      }
      private void helper (List&lt;List&lt;Integer&gt;&gt; res, List&lt;Integer&gt; cur, int n, int k, int start) {
          if (k == 0) {
              res.add(new ArrayList&lt;&gt;(cur));
              return;
          }
          for (int i = start; i &lt;= n; i++) {
              cur.add(i);
              helper(res, cur, n, k - 1, i + 1); // helper(res, cur, n, --k, i + 1)
              cur.remove(cur.size() - 1);
          }
      }
  }
  </code></pre>
  
  <p>Java. In last line 5, when I change "k - 1" to "--k", then the results will be different, can someone help me please? I think they are the same, but results are different. </p>
  
  <p>Result for "helper(res, cur, n, k - 1, i + 1);" : [[1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4]]</p>
  
  <p>Result for "helper(res, cur, n, --k, i + 1)" : [[1, 2], [2]]</p>
  
  <p>It's Leetcode 77. Combinations</p>