题解 | #石子合并#

#include <iostream>
#include <vector>
using namespace std;

int getMaxScore(int n, vector<int>& stones) {
    int maxScore = 0;
    // 计算所有可能的两两组合的乘积之和
    for(int i = 0; i < n; i++) {
        for(int j = i + 1; j < n; j++) {
            maxScore += stones[i] * stones[j];
        }
    }
    return maxScore;
}

int main() {
    int n;
    cin >> n;
    
    vector<int> stones(n);
    for(int i = 0; i < n; i++) {
        cin >> stones[i];
    }
    
    cout << getMaxScore(n, stones) << endl;
    return 0;
}

import java.util.*;

public class Main {
    static int getMaxScore(int n, int[] stones) {
        int maxScore = 0;
        // 计算所有可能的两两组合的乘积之和
        for(int i = 0; i < n; i++) {
            for(int j = i + 1; j < n; j++) {
                maxScore += stones[i] * stones[j];
            }
        }
        return maxScore;
    }
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        
        int[] stones = new int[n];
        for(int i = 0; i < n; i++) {
            stones[i] = sc.nextInt();
        }
        
        System.out.println(getMaxScore(n, stones));
    }
}

def get_max_score(n, stones):
    max_score = 0
    # 计算所有可能的两两组合的乘积之和
    for i in range(n):
        for j in range(i + 1, n):
            max_score += stones[i] * stones[j]
    return max_score

n = int(input())
stones = list(map(int, input().split()))
print(get_max_score(n, stones))