Time limit: 3.000 seconds
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=1865
A prime number is a number that has only two divisors: itself and the number one. Examples of prime numbers are: 1, 2, 3, 5, 17, 101 and 10007.
In this problem you should read a set of words, each word is composed only by letters in the rangea-z and A-Z. Each letter has a specific value, the lettera is worth 1, letter b is worth2 and so on until letter z that is worth 26. In the same way, letter A is worth 27, letterB is worth 28 and letter Z is worth52.
You should write a program to determine if a word is a prime word or not. A word is a prime word if the sum of its letters is a prime number.
The input consists of a set of words. Each word is in a line by itself and hasL letters, where 1 ≤ L ≤ 20. The input is terminated by enf of file (EOF).
For each word you should print: It is a prime word., if the sum of the letters of the word is a prime number, otherwise you should print:It is not a prime word..
UFRN contest AcM
It is a prime word. It is not a prime word. It is not a prime word.
水题。
完整代码:
/*0.009s*/ #include<cstdio> char s[25]; int main() { int i, sum; char* p; bool notprime; while (gets(s)) { sum = 0; for (p = s; *p; ++p) sum += (*p >= 'a' ? *p & 31 : (*p & 31) + 26); notprime = false; for (i = 2; i * i <= sum; ++i)///由于最大也就52*20=1040,开根号下取整就是32,所以直接算 if (sum % i == 0) { notprime = true; break; } puts(notprime ? "It is not a prime word." : "It is a prime word."); } return 0; }