AOJ

http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=34870

求n内的素数个数。

/* ***********************************************
Author        : zch
Created Time  :2015/5/19 8:46:16
File Name     :a.cpp
 ************************************************ */

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <cmath>
#include <cstdlib>
#include <ctime>
using namespace std;
typedef long long ll;
const int maxn = 1000005;
int prime[maxn];
bool is_prime[maxn];

int solve(int n) {
    int p=0;
    for(int i=0;i<=n;i++) is_prime[i]=true;
    is_prime[0]=is_prime[1]=false;
    for(int i=2;i<=n;i++) {
        if(is_prime[i])
        {
            prime[p++]=i;
            for(int j=2*i;j<=n;j+=i)
                is_prime[j]=false;
        }
    }
    return p;
}

int main()
{
    //freopen("a.txt","r",stdin);
    //freopen("b.txt","w",stdout);
    int n;
    while(~scanf("%d",&n)) {
        printf("%d
",solve(n));
    }
    return 0;
}

http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=30390

/* ***********************************************
Author        : zch
Created Time  :2015/5/19 9:53:16
File Name     :a.cpp
 ************************************************ */

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <cmath>
#include <cstdlib>
#include <ctime>
using namespace std;
typedef long long ll;
ll gcd(ll a,ll b) {
    return b==0?a:gcd(b,a%b);
}


int main()
{
    //freopen("a.txt","r",stdin);
    //freopen("b.txt","w",stdout);
    ll x,y;
    while(~scanf("%lld%lld",&x,&y)) {
        printf("%lld %lld
",gcd(x,y),x/gcd(x,y)*y);
    }
    return 0;
}