Largest Rectangle in Histogram

Given n non-negative integers representing the histogram's bar height
where the width of each bar is 1, find the area of largest rectangle in
the histogram.


Above is a histogram where width of each bar is 1, given height =
[2,1,5,6,2,3].


The largest rectangle is shown in the shaded area, which has area = 10
unit.

For example,
Given height = [2,1,5,6,2,3],
return 10.