刷题打卡，现在刷了329题。

828. Count Unique Characters of All Substrings of a Given String

1337. The K Weakest Rows in a Matrix
the fast way is the simple way, but need space.

        ans[i]=sum(mat[i])
        ans=sorted(ans, key=ans.get)

1396. Design Underground System
read the question need long time, but algo is easy.
two hash table, one for user , another for station.

{45: ('Leyton', 3)}
{45: ('Leyton', 3), 32: ('Paradise', 8)}
{45: ('Leyton', 3), 32: ('Paradise', 8), 27: ('Leyton', 10)}
defaultdict(<class 'list'>, {('Leyton', 'Waterloo'): [12]})
defaultdict(<class 'list'>, {('Leyton', 'Waterloo'): [12, 10]})

81. Search in Rotated Sorted Array II

41. First Missing Positive
this one is very hard if not use sort or extra space

            while 0 <= nums[i]-1 < len(nums) and nums[nums[i]-1] != nums[i]:
                tmp = nums[i]-1
                nums[i], nums[tmp] = nums[tmp], nums[i]

finished 356 leetcode question but i almost forget half of them now

https://www.1point3acres.com/bbs/thread-812745-1-1.html
https://www.1point3acres.com/bbs/thread-811164-1-1.html
https://www.1point3acres.com/bbs/thread-820660-1-1.html
https://www.1point3acres.com/bbs/thread-811202-1-1.html
https://www.1point3acres.com/bbs/thread-817764-1-1.html
https://www.1point3acres.com/bbs/thread-806880-1-1.html
https://www.1point3acres.com/bbs/thread-870410-1-1.html
https://www.1point3acres.com/bbs/thread-828959-1-1.html
https://www.1point3acres.com/bbs/thread-851290-1-1.html

770. Basic Calculator IV
looks very hard and too much lines code.

感觉我的存在， 就是给其他面试者当分母的。