Bug Report for https://neetcode.io/problems/minimum-stack
Please describe the bug below and include any steps to reproduce the bug or screenshots if possible.
The Problem with a Single Variable
Imagine you use a single integer variable self.min_val to track the minimum.
Let's walk through this sequence of operations:
Push 5: The stack is [5]. self.min_val = 5.
Push 3: The stack is [5, 3]. self.min_val updates to 3.
Push 7: The stack is [5, 3, 7]. self.min_val stays 3.
Now, let's call pop():
The 7 is removed. The stack is now [5, 3]. self.min_val is still 3. (This is correct).
Let's call pop() a second time:The 3 is removed. The stack is now just [5].The Crash: What should self.min_val be now? It should go back to being 5. But because 3 overwrote your single variable, your program has completely forgotten that 5 was the previous minimum!⚠️ The Rule: A single variable has no memory of history. When the current minimum is popped, you have no way of knowing what the next smallest number is without scanning the entire stack again, which forces a slow O(n)loop.
Bug Report for https://neetcode.io/problems/minimum-stack
Please describe the bug below and include any steps to reproduce the bug or screenshots if possible.
The Problem with a Single Variable
Imagine you use a single integer variable self.min_val to track the minimum.
Let's walk through this sequence of operations:
Push 5: The stack is [5]. self.min_val = 5.
Push 3: The stack is [5, 3]. self.min_val updates to 3.
Push 7: The stack is [5, 3, 7]. self.min_val stays 3.
Now, let's call pop():
The 7 is removed. The stack is now [5, 3]. self.min_val is still 3. (This is correct).
Let's call pop() a second time:The 3 is removed. The stack is now just [5].The Crash: What should self.min_val be now? It should go back to being 5. But because 3 overwrote your single variable, your program has completely forgotten that 5 was the previous minimum!⚠️ The Rule: A single variable has no memory of history. When the current minimum is popped, you have no way of knowing what the next smallest number is without scanning the entire stack again, which forces a slow O(n)loop.