02-Min-Stack.md

Min Stack

Problem Link

https://leetcode.com/problems/min-stack/

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Pattern

• Stack
• Design

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Approach

Store the current minimum alongside each pushed value so getMin stays O(1).

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Time Complexity

O(1) per operation

Space Complexity

O(n)

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Java Solution

import java.util.*;
class MinStack {
    private Stack<int[]> stack = new Stack<>();

    public void push(int val) {
        int min = stack.isEmpty() ? val : Math.min(val, stack.peek()[1]);
        stack.push(new int[]{val, min});
    }

    public void pop() {
        stack.pop();
    }

    public int top() {
        return stack.peek()[0];
    }

    public int getMin() {
        return stack.peek()[1];
    }
}