UVa 10375 Choose and divide

简单的分解质因数约分

#include <cstdio>
#include <cstdlib>
#include <cstring>

const int MAXN = 10000 + 10;

bool Prime[MAXN];

int aaa[5];
int bbb[5];
int num[2][MAXN];

void GetPrime()
{
    memset( Prime, true, sizeof(Prime) );
    Prime[0] = false ;
    Prime[1] = false ;
    for ( int i = 2; i < MAXN; i++ )
        if ( Prime[i] )
        {
            for ( int j = i * i; j < MAXN; j += i )
                Prime[j] = false;
        }
    return;
}

int cmp( const void *a, const void *b )
{
    return *(int *)a - *(int *)b;
}

int max( int a, int b )
{
    return a > b ? a : b;
}

int min( int a, int b )
{
    return a < b ? a : b;
}

void show()
{
    for ( int i = 0; i < 20; i++ )
       printf("%d ", num[0][i]);
    puts("\n---------------------");
    for ( int i = 0; i < 20; i++ )
       printf("%d ", num[1][i]);
    puts("\n----------------");
    return;
}

int main()
{
    GetPrime();
    int p, q, r, s;
    while ( scanf( "%d%d%d%d", &p, &q, &r, &s ) != EOF )
    {
        memset( num, 0, sizeof(num) );

        aaa[0] = p;
        aaa[1] = s;
        aaa[2] = r - s;
        bbb[0] = q;
        bbb[1] = r;
        bbb[2] = p - q;
        qsort( aaa, 3, sizeof(int), cmp );
        qsort( bbb, 3, sizeof(int), cmp );

//        for ( int i = 0; i < 3; i++ ) printf("%d %d\n", aaa[i], bbb[i]);

        int down, up;
        for ( int i = 0; i < 3; i++ )
        {
            int xxx;
            if ( aaa[i] == bbb[i] ) continue;
            else if ( aaa[i] > bbb[i] )
            {
                down = bbb[i] + 1;
                up = aaa[i];
                xxx = 0;
            }
            else
            {
                down = aaa[i] + 1;
                up = bbb[i];
                xxx = 1;
            }
            for ( int i = down; i <= up; i++ )
            {
                int tp = i;
    //            printf("tp = %d\n", tp);
                int yyy = 2;
                while ( tp != 1 )
                {
                    if ( Prime[yyy] && tp % yyy == 0 )
                    {
      //                  printf("yyy = %d\n", yyy);
                        tp /= yyy;
                        ++num[xxx][yyy];
                    }
                    else ++yyy;
                }
            }
        }

        for ( int i = 2; i < MAXN; i++ )
        if ( Prime[i] )
        {
            if ( num[0][i] > num[1][i] )
            {
                num[0][i] -= num[1][i];
                num[1][i] = 0;
            }
            else
            {
                num[1][i] -= num[0][i];
                num[0][i] = 0;
            }
        }

  //      show();

        double ans = 1.0;
        for ( int i = 2; i < MAXN; i++ )
            if ( Prime[i] )
            {
                int fenzi = 1, fenmu = 1;
                for ( int j = 0; j < num[0][i]; j++ ) fenzi *= i;
                for ( int j = 0; j < num[1][i]; j++ ) fenmu *= i;
                ans *= (double)fenzi/fenmu;
            }

        printf( "%.5lf\n", ans );
    }
    return 0;
}