第十三届蓝桥杯javaC组求和题伪解法

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner sc=new Scanner(System.in);int n=sc.nextInt();Long arr[]=new Long[n];for(int i=0;i<n;i++) {arr[i]=sc.nextLong();}System.out.println(c(arr));}public static Long c(Long arr[]) {Long sum=0L;if(arr.length==0) {return sum;}for(int i=0;i<arr.length;i++) {for(int j=0;j<i;j++) {sum+=arr[i]*arr[j];} }return sum;}}