[leetcode-84-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 heights = [2,1,5,6,2,3],
return 10.

思路：

查看当前值是否是递增状态，围成的矩阵面积可能会继续增加，那么继续向后遍历。

如果发生值减小，向前查看组成的面积大小。

int largestRectangleArea(vector<int>& height) {
        int res = 0;
        for (int i = 0; i < height.size(); ++i)
　　　　 {
            if (i + 1 < height.size() && height[i] <= height[i + 1])   continue;
            
            int minH = height[i];
            for (int j = i; j >= 0; --j)
　　　　　　  {
                minH = min(minH, height[j]);
                int area = minH * (i - j + 1);
                res = max(res, area);
            }
        }
        return res;
    }

参考：

http://www.cnblogs.com/grandyang/p/4322653.html