Hdu 5392 Zball in Tina town (prime)

Test instructions: (x-1)!modx (x<10^9), Goldbach conjecture, the table is suitable for the prime number of x, the result is x-1, composite when 0;X=4 is 2 Special award;

Thinking: When judging the prime number of the brain pumping, want to be a large numbers of primes, and then always tle;

When the square root of the number to be judged is the 10^8 level, consider the large number of cases ...

#include <cstdio>#include<cstring>#include<algorithm>using namespacestd;intt,n,m;intMain () {intI,j,k,flag; scanf ("%d",&t);  while(t--) {scanf ("%d",&N); if(n==4) {printf ("2\n");Continue; } Flag=0;  for(i=2; i*i<n;i++){        if(n%i==0) {flag=1; Break; }    }    if(flag) printf ("0\n"); Elseprintf"%d\n", N-1); }   return 0;}

Hdu 5392 Zball in Tina town (prime)