Prime Distance

http://poj.org/problem?id=2689

#include<iostream>
#include<cmath>
#include<vector>
#include<cstdio>
#include<string.h>
using namespace std;
typedef long long ll;
const int N = 1e5+7;
vector<ll>prime(N);
bool a[N];
int cnt = 0;
void init() {
	for(int i = 2 ; i < N ; i++) {
		if(!a[i])
			prime[cnt++] = i;
		for(int j = 0 ; j < cnt && prime[j]*i < N ; j++)
			a[prime[j]*i] = 1;
	}
	return ;
}
bool mp[N*10];
int main() {
	init();
	ll l,r;
	while(cin >> l >> r) {
		memset(mp,0,sizeof(mp));
		for(int i = 0 ; i < cnt && 1ll*prime[i]*prime[i] <= 1ll*r ; i++)
			for(int j = max(2ll,l/prime[i]) ; j*prime[i] <= r ; j++)
				mp[prime[i]*j-l]=1;
		ll pre1 = -1, len1 = 0, t1;
		ll pre2 = -1, len2 = 0x3f3f3f3f3f, t2;
		for(int i = max(2ll,l) ; i <= r ; i++) {
			if(mp[i-l])
				continue;
			if(pre1!=-1)
				if(i-pre1 > len1) {
					t1 = i;
					len1 = i-pre1;
				}
			pre1 = i;

			if(pre2!=-1)
				if(i-pre2 < len2) {
					t2 = i;
					len2 = i-pre2;
				}
			pre2 = i;
		}
		if(!len1) {
			puts("There are no adjacent primes.");
			continue;
		}
		printf("%lld,%lld are closest, %lld,%lld are most distant.\n",1ll*t2-len2,t2,1ll*t1-len1,t1);
	
	}
}

标签：Prime,Distance,cnt,int,prime,len1,include,lld
来源： https://www.cnblogs.com/zhaohanzheng/p/16069874.html