题解 | #删除字符串中出现次数最少的字符#

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Scanner;
import java.util.Map;

/**
 * HJ23 删除字符串中出现次数最少的字符
 * @author d3y1
 */
public class Main {
    public static void main(String[] args) {
        // solution1();
        // solution2();
        // solution22();
        // solution3();
        solution4();
    }

    /**
     * 字符串 + 哈希
     */
    private static void solution1(){
        Scanner in = new Scanner(System.in);
        while (in.hasNextLine()) {
            String input = in.nextLine();
            HashMap<Character,Integer> map = new HashMap<>();
            for(char ch: input.toCharArray()){
                map.put(ch, map.getOrDefault(ch,0)+1);
            }

            ArrayList<Map.Entry<Character,Integer>> list = new ArrayList<>(map.entrySet());
            Collections.sort(list, new Comparator<Map.Entry<Character, Integer>>() {
                @Override
                public int compare(Map.Entry<Character, Integer> o1, Map.Entry<Character, Integer> o2) {
                    return o1.getValue()-o2.getValue();
                }
            });
            // Collections.sort(list, (o1, o2) -> {
            //     return o1.getValue()-o2.getValue();
            // });
            // Collections.sort(list, Comparator.comparingInt(Map.Entry::getValue));

            String result = input;
            int min = list.get(0).getValue();
            char key;
            int val;
            for(Map.Entry<Character,Integer> entry: list){
                key = entry.getKey();
                val = entry.getValue();
                if(val == min){
                    result = result.replaceAll(String.valueOf(key), "");
                }else{
                    break;
                }
            }
            
            System.out.println(result);
        }
    }

    /**
     * 字符串 + 哈希
     */
    private static void solution2(){
        Scanner in = new Scanner(System.in);
        while (in.hasNextLine()) {
            String input = in.nextLine();
            HashMap<Character,Integer> map = new HashMap<>();
            for(char ch: input.toCharArray()){
                map.put(ch, map.getOrDefault(ch,0)+1);
            }

            ArrayList<Integer> list = new ArrayList<>(map.values());
            Collections.sort(list);
            int min = list.get(0);

            StringBuilder sb = new StringBuilder();
            for(char ch: input.toCharArray()){
                if(map.get(ch) != min){
                    sb.append(ch);
                }
            }

            System.out.println(sb);
        }
    }

    /**
     * 字符串 + 哈希
     */
    private static void solution22(){
        Scanner in = new Scanner(System.in);
        while (in.hasNextLine()) {
            String input = in.nextLine();
            HashMap<Character,Integer> map = new HashMap<>();
            for(char ch: input.toCharArray()){
                map.put(ch, map.getOrDefault(ch,0)+1);
            }

            ArrayList<Integer> list = new ArrayList<>(map.values());
            int min = Collections.min(list);

            StringBuilder sb = new StringBuilder();
            for(char ch: input.toCharArray()){
                if(map.get(ch) != min){
                    sb.append(ch);
                }
            }

            System.out.println(sb);
        }
    }

    /**
     * 字符串 + 哈希
     */
    private static void solution3(){
        Scanner in = new Scanner(System.in);
        while (in.hasNextLine()) {
            String input = in.nextLine();
            HashMap<Character,Integer> map = new HashMap<>();
            for(char ch: input.toCharArray()){
                map.put(ch, map.getOrDefault(ch,0)+1);
            }

            int min = Integer.MAX_VALUE;
            for(char ch: map.keySet()){
                min = Math.min(min, map.get(ch));
            }

            StringBuilder sb = new StringBuilder();
            for(char ch: input.toCharArray()){
                if(map.get(ch) != min){
                    sb.append(ch);
                }
            }

            System.out.println(sb);
        }
    }

    /**
     * 字符串 + 哈希
     */
    private static void solution4(){
        Scanner in = new Scanner(System.in);
        while (in.hasNextLine()) {
            String input = in.nextLine();
            int[] cnt = new int[26];
            for(char ch: input.toCharArray()){
                cnt[ch-'a']++;
            }

            int min = Integer.MAX_VALUE;
            for(int val: cnt){
                // 重要! val=0时 => 表明该字符从未出现
                if(val > 0){
                    min = Math.min(min, val);
                }
            }

            StringBuilder sb = new StringBuilder();
            for(char ch: input.toCharArray()){
                if(cnt[ch-'a'] != min){
                    sb.append(ch);
                }
            }

            System.out.println(sb);
        }
    }
}