HW1
- ex1: O(1)
- ex2: O(n*log(n)) n: length of list
- ex3: O(n) n: length of list 
- ex4: O(n) n: length of list
- ex5: O(n*log(n)) n: length of list
- ex6: O(n*m) n: length of list of list, m: maximum length of inner list

HW2
- ex1: O(1)
- ex2: O(n*m*log(n*m)) n: # of locations, m: maximum # of keywords
- ex3: O(n*m) n: # of locations, m: maximum # of keywords
- ex4: O(n*m) n: # of locations, m: maximum # of keywords

HW3
- ex1: O(n^2) or O(n^3) based on your implementation, n: length of list
- ex2: O(n!) n: length of list
- ex3: O(n^2*k) n: length of list, k: log(precision of floating point numbers) ~= can consider k as constant