什么是有效的算法来消除所有重复的字符串？

What is an efficient algorithm to removing all duplicates in a string?

例如： aaaabbbccdbdbcd

所需的结果： ABCD

推荐答案

您使用哈希表通过数组来存储当前发现的密钥（访问O（1）），然后循环。如果一个角色是在哈希表，丢弃它。如果它不将其添加到散列表和一个结果字符串

You use a hashtable to store currently discovered keys (access O(1)) and then loop through the array. If a character is in the hashtable, discard it. If it isn't add it to the hashtable and a result string.

总体：O（n）时间（和空间）

Overall: O(n) time (and space).

天真的解决方法是搜索字符结果字符串为您处理每一个。这为O（n 2 ）。

The naive solution is to search for the character is the result string as you process each one. That O(n2).