Primes
| Time Limit: 1000MS | Memory Limit: 65536K | |
| Total Submissions: 3204 | Accepted: 1245 |
Description
A pretty straight forward task, calculate the number of primes between 2 integers.Given 2 integers A ≤ B < 10 5 what’s the number of primes in range from A to B inclusive.
Note: A prime number is a positive integer greater than 1 and is divisible by 1 and itself only. For N to be prime it is enough to test the divisibility of numbers less than or equal to square root of N.
Input
As many as 1000 lines, each line contains 2 integers A and B separated by a space. Input is terminated when A = B = -1 (Do not process this line).Output
For every line in input except for the last line where A = B = -1 - print the number of prime numbers between A and B inclusive.Sample Input
0 9999 1 5 -1 -1
Sample Output
1229 3
#include#include #include using namespace std; bool is_prime(int n) { if(n<=0||n==1) //贡献1 WA，a，b可能小于0;so n<=0 return false; return false; for(int i=2;i<=sqrt((double)n);i++) { if(n%i==0) return false; } return true; } int main() { int a,b; int sum; while(1) { sum=0; scanf("%d%d",&a,&b); if(a==-1&&b==-1) break; for(int i=a;i<=b;i++) if(is_prime(i)) ++sum; printf("%d\n",sum); } return 0; }