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.

本题没有做出来，是参考http://blog.csdn.net/doc_sgl/article/details/11805519。

    public int largestRectangleArea(int[] height) { 
        if (height == null || height.length == 0) {
            return 0;
        }
        int len = height.length;
        int[] newHeight = new int[len + 1];
        for (int i = 0; i < len; i++) {
            newHeight[i] = height[i];
        }
        newHeight[len] = 0;
        Stack<Integer> stack = new Stack<Integer>();
        int i = 0;
        int max = 0;
        while(i < newHeight.length) {
            if (stack.isEmpty() || newHeight[stack.peek()] <= newHeight[i]) {
                stack.push(i);
                i++;
            } else {
            	while (!stack.isEmpty() && newHeight[stack.peek()] > newHeight[i]) {
                    int h = newHeight[stack.peek()];
                    stack.pop();
                    int wide;
                    if (stack.isEmpty()) {
                        wide = i;
                    } else {
                        wide = i - stack.peek() - 1;
                    }
                    int tempMax = h * wide;
                    if (max < tempMax) {
                        max = tempMax;
                    }
            	}
            	stack.push(i);
            	i++;
            }
        }
        return max;
    }