1007. Prime number pairs conjecture (20)

Time limit MS Memory limit 65536 KB code length limit 8000 B procedure StandardAuthor Chen, Yue

Let's define the DN as: DN = PN+1-PN, where pi is the number I prime. Obviously there are d1=1 and the DN for n>1 is even. "The prime number pairs conjecture" that there are infinitely many pairs of adjacent and the difference is 2 primes.

Now given any positive integer n (< 105), please calculate the number of prime pairs that do not exceed N to satisfy the conjecture.

input Format: each test input contains 1 test cases, giving a positive integer n.

output format: the output of each test case occupies one line, not exceeding N of the number of prime pairs that satisfy the conjecture.

Input Sample:

20

Sample output:

4

#include <stdio.h>#include<math.h>intMain () {intIsPrime =0; intn= -; scanf ("%d",&N); if(n>100000){        return 0; }    if(n<5) {printf ("0"); }Else{         for(intI=2; i<=n;i++){            if(Prime (i) && Prime (i)2) ) {IsPrime++; }} printf ("%d", IsPrime); }        return 0;}intPrimeintm) {    intI,n; if(m==1|| m==0){        return 0; } N=sqrt (m);  for(i=2; i<=n;i++){        if(m%i==0){            return 0; }    }    return 1;}

1007. Prime number pairs conjecture (20)