数论-质数-Goldbach's Conjecture

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水题。

#include<bits/stdc++.h>
#define rep(i,l,r) for(int i=(l);i<=(r);i++)
#define per(i,r,l) for(int i=(r);i>=(l);i--)
#define random(l,r) ((l)+rand()%((r)-(l)+1))
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
const int inf=1e9+10,N=1e6+100;
inline int read(){
	register int sign=0,v=0; register char c;
	while(!isdigit(c=getchar())) if(c=='-') break;
	if(c=='-') sign=1; else v=c-48;
	while(isdigit(c=getchar())) v=v*10+c-48;
	if(sign==0) return v; else return -v;
}
int n,v[N],prime[N],len;
void Euler(){
	rep(i,2,N){
		if(v[i]==0){
			prime[++len]=i;
			v[i]=i;
		}
		rep(j,1,len){
			if((prime[j]>v[i])||(prime[j]*i>N)) break;
			v[i*prime[j]]=prime[j];
		}
	}
}
int main(){
	Euler();
	while(n=read()){
		rep(i,1,len) if(v[n-prime[i]]==n-prime[i]){
			printf("%d = %d + %d\n",n,prime[i],n-prime[i]);
			break;
		}
	}
	return 0;
}