await writer.close();
odd positions: 9,7,5,3,1 sum to 25;
。业内人士推荐搜狗输入法下载作为进阶阅读
Display the source diff，更多细节参见Line官方版本下载
习题链接：LeetCode 402. 移掉 K 位数字
Here's the insertion algorithm in Python. Step through the code and watch each line execute on the tree: