1class Solution {2    public int largestRectangleArea(int[] heights) {3        Deque<Integer> stack = new ArrayDeque<>();4        int best = 0;5        for (int i = 0; i <= heights.length; i++) {6            int current = i == heights.length ? 0 : heights[i];7            while (!stack.isEmpty() && heights[stack.peek()] >= current) {8                int index = stack.pop();9                int left = stack.isEmpty() ? -1 : stack.peek();10                int width = i - left - 1;11                best = Math.max(best, heights[index] * width);12            }13            stack.push(i);14        }15        return best;16    }17}