黑马点评：附近商户、签到、UV 与复盘

LocalDate day = instant.atZone(businessZone).toLocalDate(); // 先按业务时区定义今天。
int bitIndex = day.getDayOfMonth() - 1; // 日期从一开始，位偏移从零开始。
boolean signed = monthBits.get(bitIndex); // 已加载月份中的显式布尔状态。
LocalDate previous = day.minusDays(1); // 日历负责跨月、跨年和闰日，不手写天数减法。

import java.time.*;
import java.util.*;
public class Main {
    record Streak(int days,String reason){}
    static BitSet bits(int... days){BitSet b=new BitSet();for(int d:days)b.set(d-1);return b;}
    static Streak streak(Map<YearMonth,BitSet> months,LocalDate today,int limit){
        if(limit<1||limit>100000)throw new IllegalArgumentException("limit");
        for(var e:months.entrySet())if(e.getKey()==null||e.getValue()==null||e.getValue().length()>e.getKey().lengthOfMonth())throw new IllegalArgumentException("month bits"); // 闰年和月份长度由日历决定。
        LocalDate day=today;int count=0;
        while(count<limit){
            BitSet b=months.get(YearMonth.from(day));if(b==null)return new Streak(count,"UNKNOWN"); // 未加载不等于没有签到。
            if(!b.get(day.getDayOfMonth()-1))return new Streak(count,"STOPPED");
            count++;if(count==limit||day.equals(LocalDate.MIN))return new Streak(count,"LIMIT");
            day=day.minusDays(1); // 自动跨越月底与闰日。
        }throw new AssertionError();
    }
    static void eq(Streak e,Streak a){if(!e.equals(a))throw new AssertionError(a);}
    public static void main(String[] args){
        LocalDate date=LocalDate.of(2024,3,1);YearMonth march=YearMonth.of(2024,3),feb=YearMonth.of(2024,2);
        eq(new Streak(3,"STOPPED"),streak(Map.of(march,bits(1),feb,bits(28,29)),date,10));
        eq(new Streak(1,"UNKNOWN"),streak(Map.of(march,bits(1)),date,10));
        eq(new Streak(0,"STOPPED"),streak(Map.of(march,bits()),date,10));
        eq(new Streak(0,"UNKNOWN"),streak(Map.of(),date,10));
        eq(new Streak(1,"LIMIT"),streak(Map.of(march,bits(1)),date,1));
        eq(new Streak(2,"STOPPED"),streak(Map.of(YearMonth.of(2025,1),bits(1),YearMonth.of(2024,12),bits(31)),LocalDate.of(2025,1,1),10));
        try{streak(Map.of(YearMonth.of(2023,2),bits(29)),LocalDate.of(2023,2,28),10);throw new AssertionError();}catch(IllegalArgumentException expected){}
        System.out.println("PASS 7 tests");
    }
}