1. 给一个数组，求，数组中的每个元素可由多少个素数组成，求总和。

注释部分代码超时了，优化后如下：

def test1():
    n = int(input())
    arr = list(map(int, input().strip().split(" ")))[:n]
    res = 0
    for i in range(n):
        res += countPrime(arr[i])
    return res


def countPrime(n):
    if n < 2:
        return 0
    count = 0
    count = n //2
    # while n >= 2:
    # n -= 2
    # count += 1
    return count


if __name__ == '__main__':
    print(test1())

3. 给一个数组，求总和和。若是和中有数字“5”，则总和为零。保证符合要求的和最大。

思路：先求总和，之后依次判断总和中的元素是否有“5”,若存在5，将最小的元素弹出并累计弹出元素和。

def test3():
    n = int(input())
    arr = list(map(int, input().strip().split(" ")))
    # n = 1
    # arr = [5]
    arr.sort(reverse=True)
    count = 0
    res = sum(arr)
    tem = res
    while tem > 0:
        if tem % 10 == 5:
            lastPop = arr.pop()
            count += lastPop
            if arr:
                res = sum(arr) + count - lastPop
                tem = res
                continue
            else:
                return 0
        tem = tem // 10
    return res


if __name__ == '__main__':
    res = test3()
    print(res)