刷题打卡贴

python 217 Contains Duplicate
set(list) O(n)

242. Valid Anagram
The question means the two words have the same components but not orders.

sql 1294. Weather Type in Each Country

178. Rank Scores

python 13. Roman to Integer

sql 574. Winning Candidate

180. Consecutive Numbers
don't filter variable in the subquery u assign values but name alias

python 122. Best Time to Buy and Sell Stock II

don't think too complicately. If the second day is higher than previous one, then sell and then buy  and add up the whole transaction

python Excel Sheet Column Number
actually calculate hex so subtitute 10 with 26

sql 578. Get Highest Answer Rate Question
get the highest rate

1132. Reported Posts II

python 387. First Unique Character in a String
class Solution:
    def firstUniqChar(self, s: str) -> int:
        c = collections.Counter(s)
        for idx, ch in enumerate(s):
            if c[ch] == 1:
                return idx
        return -1

sql 184. Department Highest Salary
SELECT d.name as Department, e.name as Employee, Salary
FROM employee e join department d on e.departmentid = d.id
WHERE (departmentid, salary) in (SELECT departmentid, max(salary)
     FROM employee
     GROUP BY 1)
   177. Nth Highest Salary

python 371. Sum of Two Integers

sql 614. Second Degree Follower

sql. 1194. Tournament Winners
we can also leverage a trick based on how MySQL handles aggregates when sql_mode=only_full_group_by is disabled (which is the case in leetcode). MySQL simple picks the first item in a row when a column is in the SELECT clause but not the GROUP BY clause. Other databases would throw an error. Therefore we can simply get the players' scores (ps) like we did in Solution 1 along with the group_id of each player by joining the subquery with the Players table. Then order them to make sure the first item of each group is what we are looking for

1225. Report Contiguous Dates


python 21. Merge Two Sorted Lists

python 350. Intersection of Two Arrays II
how should i handle duplicates?
use hash map to get each nums' values' frequency and then use built in intersection operation to get the overlaping values.

sql 1097. Game Play Analysis V

python         268        Missing Number   

118. Pascal's Triangle
first extend the original list, then shorten the list for calculation

121       
Best Time to Buy and Sell Stock   

SQL 1303. Find the Team Size

1098. Unpopular Books
in the join clause don't use between use datediff