// C++ program to find maximum rectangular area in

// linear time

#include<bits/stdc++.h>

using namespace std;

// The main function to find the maximum rectangular

// area under given histogram with n bars

int getMaxArea(int hist[], int n)

{

    // Create an empty stack. The stack holds indexes

    // of hist[] array. The bars stored in stack are

    // always in increasing order of their heights.

    stack<int> s;

    int max_area = 0; // Initialize max area

    int tp;  // To store top of stack

    int area_with_top; // To store area with top bar

                       // as the smallest bar

    // Run through all bars of given histogram

    int i = 0;

    while (i < n)

    {

        // If this bar is higher than the bar on top

        // stack, push it to stack

        if (s.empty() || hist[s.top()] <= hist[i])

            s.push(i++);

        // If this bar is lower than top of stack,

        // then calculate area of rectangle with stack

        // top as the smallest (or minimum height) bar.

        // 'i' is 'right index' for the top and element

        // before top in stack is 'left index'

        else

        {

            tp = s.top();  // store the top index

            s.pop();  // pop the top

            // Calculate the area with hist[tp] stack

            // as smallest bar

            area_with_top = hist[tp] * (s.empty() ? i :

                                   i - s.top() - 1);

            // update max area, if needed

            if (max_area < area_with_top)

                max_area = area_with_top;

        }

    }

    // Now pop the remaining bars from stack and calculate

    // area with every popped bar as the smallest bar

    while (s.empty() == false)

    {

        tp = s.top();

        s.pop();

        area_with_top = hist[tp] * (s.empty() ? i :

                                i - s.top() - 1);

        if (max_area < area_with_top)

            max_area = area_with_top;

    }

    return max_area;

}

// Driver program to test above function

int main()

{

    int hist[] = {6, 2, 5, 4, 5, 1, 6};

    int n = sizeof(hist)/sizeof(hist[0]);

    cout << "Maximum area is " << getMaxArea(hist, n);

    return 0;

}

#include 

#include 

#include 

#include 

#include  //For using min/max function.

//Above are the libraries that has been used.

​

using namespace std;

​

class largestRectangleArea {

public:

    int largestAreaInHistogram(vector<int>& histogram) {

        int n = histogram.size(); //It stores the size of histogram vector.

        if(n == 0) return 0;

        // Create an empty stack. The stack holds indexes of histogram vector.

        stack<int> st;

        st.push(-1);

        int maxarea=0;

        //Iterating over the histogram vector for finding the maximum area.

        for(int i=0;i<n;i++){

            //st.size()>1 because -1 is stored initially and size of stack is 1

            while(st.size()!=1 && histogram[st.top()]>=histogram[i]){

                int len = histogram[st.top()];

                st.pop();

                //computing the width of the rectangle forming in histogram

                int width = i-st.top()-1;

                // if the area (len*width) of the rectangle forming in histogram is greater than previous maxarea then maxarea gets updated to the greater area

                maxarea=max(maxarea,len*width);

            }

            //Pushing index in stack it helps in calculating width

            st.push(i);

        }

        //Calculating area for all the elements left in stack if it is greater than previous maxarea then update maxarea

        while(st.size()!=1){

            int in=st.top();

            st.pop();

            int w = n-st.top() -1;

            int h = histogram[in];

            maxarea = max(maxarea,w*h);

        }

        return maxarea;

    }

};

​

int main()

{

    vector<int>hist{5, 6, 4, 3, 7, 5};

    largestRectangleArea ob;

    cout << "Maximum area is " << ob.largestAreaInHistogram(hist);

    return 0;

}