新手求教一个简单问题：用qsort函数怎么为float数据排序？

经过网上搜索qsort函数用法，问题有解了!

#include<stdlib.h>

int commp(const void *a, const void *b)
{
return *(double *)a > *(double *)b ? 1 : -1;
}

main()
{
 int i;
 double a[5][2] = {2.01,0, -3.1,-3.2, 4,5, 1,1, 9.9,22};
 qsort(a, sizeof(a)/sizeof(double)/2, 2*sizeof(double ),commp);

 for(i = 0; i < sizeof(a)/sizeof(double )/2; i++)
 {
if(a[i][1] != 0)
{
printf("%lf", a[i][0]);

printf("\n");
break;
}
 }

 return 0;
 
}


-3.100000
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#include <stdio.h>
#include <stdlib.h>

int comp(const void *a,const void *b)
{
    return ((float *)a)[0] > ((float *)b)[0] ? 1 : -1;
}

main()
{
    float a[5][2]={2.01,0, 3.1,-3.2, 4,5, 1,1, 9.9,22};
    qsort(a,5, sizeof(float)*2, comp);
    int i,j;
    for (i=0; i<5; i++)
    {
        for (j=0; j<2; j++)
            printf("%.2f ", a[i][j]);
        printf("\n");
    }
}

看三楼的贴我莫名其妙地笑了~

#include<stdio.h>                    
                    
#include<stdlib.h>                    
                    
int commp(const void *a, const void *b)                    
{                    
  return ((float *)a)[0] - ((float *)b)[0];                    
}                    
                    
main()                    
{   
    int i = 0;               
    float a[5][2] = {2.01,0, -3.1,-1, 4,5, 1,-1, 9.9,22};   
                  
    qsort(a, sizeof(a)/sizeof(float)/2, 2*sizeof(float ),commp);                    
                    
    for(i = 0; i < sizeof(a)/sizeof(float )/2; i++)                    
    {                    
       if(a[i][1] != 0)                    
       {                    
          printf("%-6.2f%-6.2f", a[i][0], a[i][1]);
          printf("\n");      
          if(a[i][1] == a[i+1][1])
          printf("%-6.2f%-6.2f", a[i+1][0], a[i+1][1]);

          printf("\n");               
          break;                    
       }                    
    }                    
                    
    return 0;   
 }

-3.10 -1.00
1.00  -1.00
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sizeof(a)/sizeof(a[0])~比较好看结果都是5~