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题解 | 统计复旦用户8月练题情况

select u.device_id, university, count(question_id) as question_cnt, sum( case when result = 'right' then 1 ...

2025-09-11

1 24

题解 | 截取出年龄

select regexp_substr(profile,'[0-9]+',1,3) as age, count(*) as number from user_submit group by age;

2025-09-10

1 40

题解 | 提取博客URL中的用户名

select device_id, regexp_substr(blog_url,'[^/]+$') as user_name from user_submit;

2025-09-10

1 31

题解 | 统计每种性别的人数

select regexp_substr(profile,'male|female') as gender, count(*) as number from user_submit group by gender;

2025-09-10

1 31

题解 | 计算用户的平均次日留存率

SELECT -- 计算留存的用户天数 / 总的用户活跃天数 COUNT(t2.device_id) / COUNT(t1.device_id) AS avg_ret FROM -- t1 代表所有用户活跃的记录 (去重) (SELECT DISTINCT devic...

2025-09-10

1 27

题解 | 判断一个链表是否为回文结构

# class ListNode: # def __init__(self, x): # self.val = x # self.next = None # # 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可 # # # @para...

2025-09-10

1 33

题解 | 宝石计数

# # 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可 # # # @param jewels string字符串 # @param stones string字符串 # @return int整型 # class Solution: def numJewel...

2025-09-10

1 22

题解 | 数对计数

import sys from collections import defaultdict def main(): data = sys.stdin.read().split() n = int(data[0]) c = int(data[1]) arr = li...

2025-09-09

1 31

题解 | 参议院投票

# # 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可 # # 求出最终获胜帮派的名称 # @param s string字符串 # @return string字符串 # from collections import deque class Solution: ...

2025-09-08

1 34

题解 | 用两个栈实现队列

# -*- coding:utf-8 -*- class Solution: def __init__(self): self.stack1 = [] self.stack2 = [] def push(self, node): # w...

2025-09-08

1 50