Overview
Occurrences count karna: list ya string mein har element kitni baar aata hai yeh count karo.
Analogy
Jaise paragraph mein har word ko count karo.
Step-by-step
- Khaali dictionary banao
- Har element par loop karo
- Agar exist karta hai toh +1, warna 1 se initialize karo
- Ya collections.Counter use karo
Visual
lst = [1,2,2,3,3,3]
cnt = {}
for x in lst:
cnt[x] = cnt.get(x,0)+1
# {1:1, 2:2, 3:3}
Common mistakes
- .get() ke bina [] se KeyError aata hai
- Counter initialize karna bhool jana
Practice questions
- String mein har character count karo
- Sabse zyada frequent element dhundo
Space
O(k) k unique keys ke liye