important_dsa_problems/Getmin()_stack.cpp at main · arinyadav/important_dsa_problems · GitHub

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GFG
 love babbar approach :--
#include<stack>
#include<limits.h>
class SpecialStack {
    // Define the data members.
	stack<int> s;
    int mini = INT_MAX;
    /*----------------- Public Functions of SpecialStack -----------------*/
    public:

    void push(int data) {
        //for first element
        if(s.empty()) {
            s.push(data);
            mini = data;
        }
        else
        {
         	if(data < mini) {
                s.push(2*data - mini);
                mini = data;
            }
            else
            {
                s.push(data);
            }
        }
    }

    int pop() {
        if(s.empty()){
            return -1;
        }

        int curr = s.top();
        s.pop();
        if(curr > mini) {
            return curr;
        }
        else
        {
            int prevMin = mini;
            int val = 2*mini - curr;
            mini = val;
            return prevMin;
        }
    }

    int top() {
        if(s.empty())
            return -1;

        int curr = s.top();
        if(curr < mini) {
            return mini;
        }
        else
        {
            return curr;
        }
    }

    bool isEmpty() {
        return s.empty();
    }

    int getMin() {
        if(s.empty())
            return -1;

        return mini;
    }
};


ANother Approach

 int minEle;
    stack<int> s;
    public:

       /*returns min element from stack*/
       int getMin(){
           if(s.empty())return -1;
           return minEle;
           //Write your code here
       }

       /*returns poped element from stack*/
       int pop(){
           if(s.empty())return -1;
           int t=s.top();s.pop();
           if(t>=0)return t+minEle;
           else{
               int x=minEle;
               minEle=minEle-t;
               return x;
           }
           //Write your code here
       }

       /*push element x into the stack*/
       void push(int x){
           if(s.empty())minEle=x;
           int t=x-minEle;
           s.push(t);
           minEle=min(minEle,x);
           //Write your code here
       }