Given a string s, remove duplicate letters so that every letter appears once and only once. You must make sure your result is the smallest in lexicographical order among all possible results.
\n
Example 1:
\n\n\nInput: s = "bcabc"\nOutput: "abc"\n\n\n
Example 2:
\n\n\nInput: s = "cbacdcbc"\nOutput: "acdb"\n\n\n
\n
Constraints:
\n\n1 <= s.length <= 104s consists of lowercase English letters.\n
Note: This question is the same as 1081: https://leetcode.com/problems/smallest-subsequence-of-distinct-characters/
\n", "translatedTitle": "去除重复字母", "translatedContent": "给你一个字符串 s ，请你去除字符串中重复的字母，使得每个字母只出现一次。需保证 返回结果的字典序最小（要求不能打乱其他字符的相对位置）。
\n\n
示例 1：
\n\n\n输入：\n\ns = \"bcabc\"\n输出：\"abc\"\n
示例 2：
\n\n\n输入：\n\ns = \"cbacdcbc\"\n输出：\"acdb\"
\n\n
提示：
\n\n1 <= s.length <= 104s 由小写英文字母组成\n\n
注意：该题与 1081 https://leetcode-cn.com/problems/smallest-subsequence-of-distinct-characters 相同
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