Largest Rectangle in Histogram

Given an array of integers A of size N. A represents a histogram i.e A[i] denotes height of
the i^th histogram’s bar. Width of each bar is 1.

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.

Find the area of largest rectangle in the histogram.

Input Format

The only argument given is the integer array A.

Output Format

Return the area of largest rectangle in the histogram.

For Example

Input 1:
    A = [2, 1, 5, 6, 2, 3]
Output 1:
    10
    Explanation 1:
        The largest rectangle is shown in the shaded area, which has area = 10 unit.

NOTE: You only need to implement the given function. Do not read input, instead use the arguments to the function. Do not print the output, instead return values as specified. Still have a doubt? Checkout Sample Codes for more details.