AOJ - 0009 Prime Number (素数筛法） && AOJ - 0005 (求最大公约数和最小公倍数)

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 = ;
 int prime[maxn];
 bool is_prime[maxn];

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

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==?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\n",gcd(x,y),x/gcd(x,y)*y);
     }
     return ;
 }