1666.組合+判斷素數

中文English

給定n個整數和一個整數k, 你可以從中選擇k個整數, 現在，要求你計算出k個數和為素數共有多少種方案。

樣例

樣例 1:

輸入：a=[3,7,12,19]，k=3
輸出：1
解釋：
There are 4 ways
3+7+12=22　　3+7+19＝29　　7+12+19＝38　　3+12+19＝34  
and only 29 is a prime.

樣例 2:

輸入：a=[1,2,3], k=2
輸出：2
解釋：
There are 3 ways
1 + 2 = 3         1 + 3 = 4      2 + 3 =5
and only 3 and 5 are primes.
 

注意事項

n不超過1010
k不超過n

class Solution:
    """
    @param a: the n numbers
    @param k: the number of integers you can choose
    @return: how many ways that the sum of the k integers is a prime number
    """
    def getWays(self, a, k):
        # Write your code here
        #首先找到所有的組合，for迴圈內嵌dfs，然後給出子函式，判斷是否是素數
        
        results 
 
= []
        self.getAllArray(results, a, [], k)
        count = 0 
        
        #print(results)
        for result in results:
            if self.isPrime(result):
                count += 1 
        
        return count
        
    #遞迴的傳參
    def getAllArray(self,results, a, array, k):
    
        #遞迴的出口
        
 
if (k == 0):
            results.append(sum(array))
        
        #遞迴的拆解
        for i in range(len(a)):
            self.getAllArray(results, a[i + 1: ], array + [a[i]], k - 1)
        
    
    def isPrime(self, num):
        for i in range(2, num):
            if num % i == 0:
                return False
        
        return True