题解：Digit Primes（数字素数）

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最新推荐文章于 2022-12-05 17:16:20 发布 · 802 阅读

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本问题要求找出在指定范围内（小于1000000）的数字素数数量。数字素数是其数字之和也构成素数的素数。例如，41是一个数字素数，因为4+1=5，而5是素数。题目提供输入文件，包含多个测试用例，每个用例给出两个整数t1和t2，需要计算t1到t2（含）之间的数字素数个数。

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A prime number is a positive number, which is divisible by exactly two diﬀerent integers. A digit prime is a prime number whose sum of digits is also prime. For example the prime number 41 is a digit prime because 4 + 1 = 5 and 5 is a prime number. 17 is not a digit prime because 1 + 7 = 8, and 8 is not a prime number. In this problem your job is to ﬁnd out the number of digit primes within a certain range less than 1000000.
Input First line of the input ﬁle contains a single integer N (0 < N ≤ 500000) that indicates the total number of inputs. Each of the next N lines contains two integers t1 and t2 (0 < t1 ≤ t2 < 1000000).
Output
For each line of input except the ﬁrst line produce one line of output containing a single integer that indicates the number of digit primes between t1 and t2 (inclusive).
Sample Input
3 10 20 10 100 100 10000
Sample Output
1 10 576
Note: You should at least use scanf() and printf() to take input and produce output