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.

class Solution {
public:
    int largestRectangleArea(vector<int>& height) {
        height.push_back(0);
        int result = 0;
        int n = height.size();

        stack<int> buf;
        for (int i = 0; i < n; i++)
        {
            while (!buf.empty() && height[i] < height[buf.top()])
            {
                int top = buf.top();
                buf.pop();
                int left = buf.empty()? -1 : buf.top();
                int temp = (i-left-1)*height[top];
                if (temp > result)
                {
                    result = temp;
                }
            }

            buf.push(i);
        }

        return result;
    }
};