poj 1942 Paths on a Grid

简单的组合题：

View Code

#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;

LL Gcd( LL a, LL b )

{

   return b ==0 ? a : Gcd( b , a % b );    

}

LL Get_C( LL n ,LL m )

{

   LL ans = 1,ans1 = 1;

   while( m )

   {

      ans *= n;

      ans1 *=m;

      LL t = Gcd( ans ,  ans1 );

      ans /= t;

      ans1 /= t;

      n --;

      m --;

   }    

   return ans/ans1;

}

int main(  )

{

    LL n,m;

    while( scanf( "%I64d %I64d",&n,&m ),n|m )

    {

          printf( "%I64d\n",Get_C( n+m ,min( n , m ) ) );    

    }

    //system( "pause" );

    return 0;

}