题解 | #石子合并#

与其他人的没什么区别，只是用stream

import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] w = new int[n];
        for(int i=0;i<n;i++) {
            w[i] = scanner.nextInt();
        }
        final int sum = Arrays.stream(w).sum();
        int score = Arrays.stream(w).map(e->e*(sum-e)).sum() /2;
        System.out.println(score);
    }
}