84.柱状图的最大矩形

84. 柱状图中最大的矩形 - 力扣（LeetCode）

注意首尾加0的细节就可

class Solution {
   
    public int largestRectangleArea(int[] heights) {
       
        Deque<Integer> stack = new LinkedList<>();
        int[] newHeight = new int[heights.length + 2];
        System.arraycopy(heights, 0, newHeight, 1, heights.length);
        newHeight[heights.length+1] = 0;
        newHeight[0] = 0;
        int res = 0;
        for(int i = 0;i<newHeight.length;i++){
            while(!stack.isEmpty()&&newHeight[i]<newHeight[stack.peek()]){
                int right = i;
                int mid = stack.pop();
                int left = stack.peek();
                int h = newHeight[mid];
                int w = right-left-1;
               
                res = Math.max(res,h*w);
            }
            stack.push(i);
        }
        return res;
    }
}