84 Largest Rectangle in Histogram

参考 ： http://www.cnblogs.com/lichen782/p/leetcode_Largest_Rectangle_in_Histogram.html

    public int largestRectangleArea(int[] height)  {
        int i = 0;
        int maxArea = 0;
        int[] h = new int[height.length + 1];
        h = Arrays.copyOf(height, height.length + 1);
        Stack<Integer> stack = new Stack<Integer>();

        while (i < h.length) {
            if (stack.isEmpty() || h[stack.peek()] <= h[i]) {
                stack.push(i++);
            } else {
                int t = stack.pop();
                maxArea = Math.max(maxArea, h[t]*(stack.isEmpty() ? i : i - stack.peek() - 1));
            }
        }
        return maxArea;
    }