日期范围内具有重复日期的FInd最小日期

from collections import defaultdict

def find_min_duplicate_date(dates, start_date, end_date):
    date_count = defaultdict(int)
    min_duplicate_date = None
    
    for date in dates:
        if start_date <= date <= end_date:
            date_count[date] += 1
            if date_count[date] == 2 and (min_duplicate_date is None or date < min_duplicate_date):
                min_duplicate_date = date
    
    return min_duplicate_date

# 示例数据
dates = ['2023-01-01', '2023-01-02', '2023-01-03', '2023-01-02', '2023-01-04']
start_date = '2023-01-01'
end_date = '2023-01-04'

min_duplicate_date = find_min_duplicate_date(dates, start_date, end_date)
print(f"最小重复日期是: {min_duplicate_date}")