题解 | 字符集合

#include <bits/stdc++.h>
using namespace std;

class Solution {
public:
    string removeDuplicates(const string& str) {
        string result;
        unordered_set<char> seen;
        
        for (char c : str) {
            if (seen.find(c) == seen.end()) {
                result += c;
                seen.insert(c);
            }
        }
        
        return result;
    }
};

int main() {
    string line;
    Solution solution;
    
    while (getline(cin, line)) {
        cout << solution.removeDuplicates(line) << endl;
    }
    
    return 0;
}

import java.util.*;

public class Main {
    static class Solution {
        public String removeDuplicates(String str) {
            StringBuilder result = new StringBuilder();
            Set<Character> seen = new HashSet<>();
            
            for (char c : str.toCharArray()) {
                if (!seen.contains(c)) {
                    result.append(c);
                    seen.add(c);
                }
            }
            
            return result.toString();
        }
    }
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Solution solution = new Solution();
        
        while (sc.hasNextLine()) {
            String line = sc.nextLine();
            System.out.println(solution.removeDuplicates(line));
        }
        
        sc.close();
    }
}

class Solution:
    def remove_duplicates(self, s: str) -> str:
        seen = set()
        result = []
        
        for c in s:
            if c not in seen:
                result.append(c)
                seen.add(c)
                
        return ''.join(result)

if __name__ == "__main__":
    solution = Solution()
    
    while True:
        try:
            line = input().strip()
            print(solution.remove_duplicates(line))
        except EOFError:
            break