2364. Count Number of Bad Pairs
Permutation: in order. n!/(n – m)! Combination: order not considered. n!/((n – m)! * m!) Key point of this problem is to transfer i…
Tag: Hash Table
916. Word Subsets
Instead of dictionary, we can use an array of 26. Every medium has it’s own easy and hard…
3404. Count Special Subsequences
Point: Turn multiplication to fraction Hard to realize “for r in range(4, n – 2): q = r – 2” part.
2168. Unique Substrings With Equal Digit Frequency
Actually, brute force can work due to constrains. However, if we count the frequency every time, the time complexity will be O(n**3), which may…
3408. Design Task Manager
Point is: we don’t have to remove items immediately from heap after rmv / edit operation. Do it when we are going to execTop.
