Maximize the rectangular area under Histogram

Question

I have a histogram with integer heights and constant width 1. I want to maximize the rectangular area under a histogram. e.g.:

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Answer 1

I coded this one and felt little better in the sense:

import java.util.Stack;

     class StackItem{
       public int sup;
       public int height;
       public int sub;

       public StackItem(int a, int b, int c){
           sup = a;
           height = b;
           sub =c;
       }
       public int getArea(){
           return (sup - sub)* height;
       }


       @Override
       public String toString(){
       return "     from:"+sup+
              "     to:"+sub+
              "     height:"+height+              
              "     Area ="+getArea();
       }
    }   


public class MaxRectangleInHistogram {    
    Stack S;
    StackItem curr;
    StackItem maxRectangle;

    public StackItem getMaxRectangleInHistogram(int A[], int n){
        int i = 0;
        S = new Stack();        
        S.push(new StackItem(0,0,-1));
        maxRectangle = new StackItem(0,0,-1);

        while(i S.peek().height){
                            S.push(curr); 
                    }else if(curr.height == S.peek().height){                            
                            S.peek().sup = i+1;                         
                    }else if(curr.height < S.peek().height){                            

                            while((S.size()>1) && (curr.height<=S.peek().height)){
                                curr.sub = S.peek().sub;
                                S.peek().sup = i;
                                decideMaxRectangle(S.peek());
                                S.pop(); 
                            }                               
                        S.push(curr);                    
                    }
            i++;
        }

        while(S.size()>1){ 
            S.peek().sup = i;
            decideMaxRectangle(S.peek());
            S.pop();            
        }  

        return maxRectangle;
    }

    private void decideMaxRectangle(StackItem s){ 

        if(s.getArea() > maxRectangle.getArea() )
            maxRectangle = s;      
    }

}

Just Note:

Time Complexity: T(n) < O(2n) ~ O(n)
Space Complexity S(n) < O(n)