哈希表

这里使用数组代替哈希表，开销更小，性能更好

import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out);

        char[] arr = br.readLine().toCharArray();
        // 统计每个字母出现的次数
        int[] freq = new int[26];
        for (char c : arr) {
            freq[c - 'a']++;
        }
        // 最小次数
        int minFreq = arr.length;
        for (int f : freq) {
            if (f > 0)
                minFreq = Math.min(minFreq, f);
        }

        for (char c : arr) {
            // 跳过出现次数最少的字符
            if (freq[c - 'a'] == minFreq) {
                continue;
            }
            pw.print(c);
        }
        pw.println();

        pw.flush();
        pw.close();
        br.close();
    }
}