#include <iostream.h> #include <malloc.h> #include <stdlib.h>   typedef struct date {        int a;        int b; }Date;   int check(int b,int a)//  b/a是否是真分数 {        int i;        for(i=2;i<=b;i++)        if(a%i==0 && b%i==0)               return 0;        return 1; }   int cmp(const void *a , const void *b ) {        struct date *c = (struct date *)a;        struct date *d = (struct date *)b;        float x,y;        x=(float)(c->b)/c->a;        y=(float)(d->b)/d->a;        if(x-y>0)        return 0;        return 1; }   void FareySequence(int n)//, char farey[]) {        int i,j;        int total=0;        Date *s;        s=(struct date * )malloc(n*n*sizeof(struct date));        for(i=2;i<=n;i++)        {               for(j=1;j<i;j++)               {                      if(check(j,i)==1)                      {                             s[total].a=i;                             s[total].b=j;                             total++;                      }               }        }        qsort(s,total,sizeof(s[0]),cmp);        for(i=0;i<total;i++)        cout<<s[i].b<<"~"<<s[i].a<<" "; }   int main() {        int n;        //char *farey;        cin>>n;        FareySequence(n); }  

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