Overview
Queue FIFO (First In First Out) structure hai jisme enqueue aur dequeue operations hain.
Analogy
Jaise supermarket mein queue—jo pehle aaya woh pehle serve hota hai.
Step-by-step
- enqueue queue ke tail mein element add karta hai
- dequeue head element delete karke return karta hai
- peek head dekhta hai
- is_empty check karta hai khaali hai ya nahi
Visual
from collections import deque
q = deque()
q.append(1) # enqueue
q.append(2)
q.popleft() # dequeue → 1
q[0] # peek → 2
Common mistakes
- List se queue banane par pop(0) O(n) hai
- deque aur list ka fark nahi jaanna
Practice questions
- BFS ke liye queue implement karo
- Queue se string mein pehla non-repeating character nikalo