DAY16P2.md

Min Stack

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• Question:

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

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• Example:

Input ["MinStack","push","push","push","getMin","pop","top","getMin"] [[],[-2],[0],[-3],[],[],[],[]]

Output [null,null,null,null,-3,null,0,-2]

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• Solution:

Code :

class MinStack {
    Stack<Integer> st=new Stack<>();
    int min=Integer.MAX_VALUE;
    public void push(int val) {
        if(val<=min)
        {
            st.push(min);
            min=val;
        }
        st.push(val);
    }
    
    public void pop() {
        if(st.peek()==min)
        {
            st.pop();
            min=st.pop();
        }
        else
        {
            st.pop();
        }
    }
    
    public int top() {
        return st.peek();
    }
    
    public int getMin() {
        return min;
    }
}