Python Tricks for Competitive Programming
1. Sort List of Tuples by Second Value in Reverse Order
val = [('v', 3), ('a', 4), ('b', 2)]
val.sort(key = lambda x: x[1], reverse=True)
print(val)
Reference: Sort List of Tuples by First/Second value
2. List of Cubes of First 5 Odd Numbers using List Comprehension
arr = [i*3 for i in range(10) if i%2]
print(arr)
3. Python Dictionary Comprehension
dic = [(i, i*2) for i in range(10)]
print(dict(dic))
4. Python Map Example
print(list(map(lambda x: x*2, range(10))))
Reference: Lambda Function
5. Python Filter Example
print(list(filter(lambda x: x%2, range(10))))
6. Python Reduce Example
from functools import reduce
print(reduce(lambda x,y: x+y, range(10)))
7. Permutation
import itertools
itertools.permutations('ABCD', 2)
Reference: Get permutation of a string
8. Selecting Random Number
import random
print(random.choice(range(1, 10)))
Reference: Selecting random number
9. Get the Frequency of Characters in String
Using Collection Counter
from collections import Counter
print(dict(Counter("ababacd")))
#Counter({'a': 3, 'b': 2, 'c': 1, 'd': 1})
Using List Comprehension
msg = "ababcd"
dic = [(i, msg.count(i)) for i in set(msg)]
print(dict(dic))
#{'c': 1, 'b': 2, 'd': 1, 'a': 2}
10. Convert Python Dict to List
dic = {'a': 3, 'b': 2, 'c': 1, 'd': 1}
# list of dictionary keys
print(list(dic))
# list of dictionary values
print([v for k, v in dic.items()])
11. Convert Integer to Binary String
num = 9
binary_num = bin(num).replace("0b", "") #1001
These Python Tricks for Competitive Programming will help you for solving competitive coding challenges in coding interviews.
