[5,0,2,1,4,0,1,0,3]

17

import java.util.*;
public class Main{
    public static void main(String[] args){
        int[] height = new int[]{5,0,2,1,4,0,1,0,3};
        System.out.println(qingdou(height));
    }
    static int qingdou(int[] w){
        Stack<Integer> stack = new Stack<>();
        int res = 0;
        //單調棧
        for(int i = 0; i < w.length; i++){            
            int last = 0; //上一個棧頂元素
            while(!stack.empty() && w[stack.peek()] <= w[i]){
                res += (w[stack.peek()] - last) * (i - stack.peek() - 1);
                last = w[stack.peek()];
                stack.pop();
            }
            if(!stack.empty()) {
                res += (w[i] - last) * (i - stack.peek() - 1);
            }
            stack.push(i);
        }
        return res;
    }
}