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#include<stdio.h>
#include<math.h>
int cc(long int a);
int main(void){
        long int a;
        while(scanf("%ld",&a)!=EOF){
            if(a==0)break;
            else if(a%2==1)
                printf("Goldbach's conjecture is wrong.\n");
            else
                for(long int i=3;i<a/2+1;i+=2)
                    if(cc(i)==0&&cc(a-i)==0){
                        printf("%ld = %ld + %ld\n",a,i,a-i);
                        break;
                    }
        }
        return 0;
}
int cc(long int a){
        for(long int i=3;i<=pow(a,1/2.0);i+=2)
            if(a%i==0)return 1;
        return 0;
}
希望厲害的高手們能幫忙看看 

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建個質數表就能過了...

 

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建質數表+二分搜尋數