HDU 4135 Co-prime

简单的容斥定理的运用：

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#include<iostream>

#include<cstdio>

#include<cstdlib>

#include<algorithm>

#include<cmath>

#include<queue>

#include<set>

#include<map>

#include<cstring>

#include<vector>

#include<string>

#define LL long long

using namespace std;

int prime[10000],cnt=0;

LL factor[40];

void Prime( )

{

     bool hash[50024] = { 0 };

     int t = ( int )sqrt( 100000.0 ) + 1;

     for( int i = 3 ; i <= t ; i += 2 ){

          if( !hash[i>>1] )

          {

              int x = i << 1;

              for( int j = i * i ; j <= 100000 ; j += x )

                   hash[j>>1] = true;

          }        

     }

     prime[cnt++] = 2;

     for( int  i = 1 ; i <= 50000 ; i ++ ){

          if( !hash[i] )

              prime[cnt++] = ( i << 1 ) + 1;            

     }

}

int Get_Factor( LL num  )

{

    int count = 0;

    for( int i = 0 ; i < cnt ; i ++ )

    {

         if( num < prime[i] ) break;

         if( num % prime[i] == 0 )

         {

             factor[count++] = prime[i];

             while( num % prime[i] == 0 )

                    num /= prime[i];

         }    

    }    

    if( num != 1 ) factor[count++] = num;

    return count;

}

LL DFS( LL num , int start ,int count)

{

    LL ans = 0;

    for( int i = start ; i < count ; i ++ )

         ans += num /(LL) factor[i] - DFS( num /(LL) factor[i] , i + 1 , count );

    return ans;    

}

int main(  )

{

    Prime();

    int T;

    LL A,B,N;

    while( scanf( "%d",&T )==1 )

    {

         for( int i = 1 ;i <= T ; i ++ )

         {

              

              LL ans1 = 0,ans2 = 0;

              scanf( "%I64d %I64d %I64d",&A,&B,&N );

              if( N == 1 ) {

                    printf( "Case #%d: %I64d\n",i,B -A +1 );

                    continue;

              }

              int count = Get_Factor( N );    

              ans1 = B  - DFS( B , 0 ,count );

              ans2 = A - 1  - DFS( A-1 , 0, count );

              printf( "Case #%d: %I64d\n",i,ans1 - ans2 );

         }    

    }

    //system( "pause" );

    return 0;

}