题解 | #数列求和#

public class Main {
    public static void main(String[] args) {

        //write your code here........
        long[] arr = new long[10];
        long sum =9;
        arr[0]=9;
        for(int i=1 ;i<10 ;i++){
            arr[i] = arr[i-1]+9*(long)(Math.pow(10,i));
            sum+=arr[i];
        }
        System.out.print(sum);
    }
}