POJ 3518 Prime Gap (Prime question)

"Test Instructions": Enter a number, assuming that the number is a prime on the output 0, assuming that the prime is not the output from its recent two prime number difference, called Prime Gap.

"Analysis": This problem is very risky. Because I was hitting the primes table.

Since the maximum prime number is 1299709, be careful to use a long long when hitting the table. Otherwise the program should not execute. Note that this should be possible.

Accumulation!

2984K 235Ms #include <iostream>using namespace std; #define N 2000001bool isprime[n];  Long long prime[100001],nprime;  Note Long long  void Doprime ()  {      long long i,j;  // !! Note    nprime = 1;      memset (isprime,true,sizeof (IsPrime));      ISPRIME[1] = 0;      for (i = 2;i<=1299709;i++)      {          if (Isprime[i])          {              prime[nprime++] = i;              for (j = i*i;j<=1299709;j+=i)              {                  Isprime[j] = false;             }          }      }  

POJ 3518 Prime Gap (Prime question)