累加列表中第n个元素之前的元素

def sum_before_n(lst, n):
    sum = 0
    for i in range(n):
        sum += lst[i]
    return sum

# 示例用法
lst = [1, 2, 3, 4, 5]
n = 3
result = sum_before_n(lst, n)
print(result)  # 输出6，即1 + 2 + 3

public class SumBeforeN {
    public static int sumBeforeN(int[] arr, int n) {
        int sum = 0;
        for (int i = 0; i < n; i++) {
            sum += arr[i];
        }
        return sum;
    }

    // 示例用法
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        int n = 3;
        int result = sumBeforeN(arr, n);
        System.out.println(result);  // 输出6，即1 + 2 + 3
    }
}