# C++ Program to Find Largest Rectangular Area in a Histogram

This is a C++ Program to find largest Rectangular Area in a Histogram

## Algorithmof function getArea():

Begin
Create an empty stack.
Initialize the largest_area.
Do a while loop start from first bar for every bar hist[i], where i = 0 to
less than n:
If stack is empty or hist[i] is higher than the bar at top of stack, then
push ‘i’ to stack.
Else
this bar is smaller than the top of stack, then keep removing the
top of stack while top of the stack is greater. Calculate area of
rectangle with smallest bar. Element before top in stack is left
index and i is right index for the top.
Pop the remaining bars from stack if stack is not empty and calculate
area with every popped bar as the smallest bar.
End

## Example Code

#include<iostream>
#include<stack>
using namespace std;
int getArea(int hist[], int n)
{
stack<int> st;
int largest_area = 0;
int top;
int toparea;
int i = 0;
while (i < n)
{
if (st.empty() || hist[st.top()] <= hist[i])
st.push(i++);
else
{
top = st.top();
st.pop();
toparea = hist[top] * (st.empty() ? i :
i - st.top() - 1);
if (largest_area < toparea)
largest_area = toparea;
}
}
while (st.empty() == false)
{
top = st.top();
st.pop();
toparea = hist[top] * (st.empty() ? i :
i - st.top() - 1);
if (largest_area < toparea)
largest_area = toparea;
}
return largest_area;
}
int main()
{
int hist[] = {6,7,4,5,3,2};
int n = sizeof(hist)/sizeof(hist);
cout << "Largest area is " << getArea(hist, n);
return 0;
}

## Output

Largest area is 16