Explain queue from stacks.
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01
Understand the problem
stackqueue
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02
Attempt it yourself
Sketch your approach before reading the solution — that's what interviews test.
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03
03
Study the solution
The solution is waiting
Give it an honest attempt first — then compare your thinking with the full walkthrough.
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04
Read the code
Queue via in/out stacks
Run Playgroundclass MyQueue:
def __init__(self):
self.in_stack = []
self.out_stack = []
def enqueue(self, x):
self.in_stack.append(x)
def dequeue(self):
self._shift()
return self.out_stack.pop()
def peek(self):
self._shift()
return self.out_stack[-1]
def _shift(self):
if not self.out_stack:
while self.in_stack:
self.out_stack.append(self.in_stack.pop())
# --- demo ---
q = MyQueue()
q.enqueue(1); q.enqueue(2); q.enqueue(3)
print(q.dequeue()) # 1
print(q.dequeue()) # 2
q.enqueue(4)
print(q.dequeue()) # 305
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