usaco 2.1 frac1...辗转相除+bubble sort...

/*
    ID:chenjiong
    PROG:frac1
    LANG:C++
*/

#include <stdio.h>
#include <string.h>

const int MAXN = 160;

typedef struct {
    int x;
    int y;
}FRAC;

int N;
FRAC table[MAXN * MAXN / 2];
int cnt;

int gcd(int a,int b)
{
    // a >= b
    if ( b == 0 )
        return a;
    else
        return gcd(b,a % b);
}

void generate()
{
    int i,j;
    for ( i = 1; i <= N; i++)
    {
        for ( j = 0; j <= i; j++)
        {
            if ( gcd(i,j) == 1 )
            {
                table[cnt].x = j;
                table[cnt].y = i;
                cnt++;
            }
        }
    }
}

int cmp(FRAC p,FRAC q)
{
    return p.x * q.y - q.x * p.y;
}

void swap(FRAC& a,FRAC& b)
{
    FRAC t = a;
    a = b;
    b = t;
}

void bubble_sort()
{
    int i,j;
    for ( i = 1; i <= cnt - 1; i++)
    {
        for ( j = 0; j <= cnt - 1 - i; j++)
        {
            if ( cmp(table[j],table[j + 1]) > 0 )
                swap(table[j],table[j + 1]);
        }
    }
}

int main()
{
    freopen("frac1.in","r",stdin);
    freopen("frac1.out","w",stdout);

    scanf("%d",&N);

    generate();
    bubble_sort();

    int i;
    for ( i = 0; i < cnt; i++)
        printf("%d/%d\n",table[i].x,table[i].y);

    return 0;
}