[此贴子已经被作者于2017-1-25 18:34编辑过]

这个程序可以正确运行：

#include<stdio.h>                                
                                
#include<stdlib.h>                                
                                
int commp(const void *a, const void *b)                                
{                                
return *(float *)a > *(float *)b ? 1 : -1;                                
}                                
                                
main()                                
{                                
 int i;                                
 float a[9][2] = {1,2,-7,7,-6,6,5,-5,2.01,0, -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("%f", a[i][0]);                                
if(a[i][1] == a[i+1][1])                                
printf("%f", a[i+1][0]);                                
                                
printf("\n");                                
break;                                
}                                
 }                                
                                
 return 0;                                
                                 
}                                



-7.000000
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[此贴子已经被作者于2017-1-25 18:42编辑过]

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

                      

[此贴子已经被作者于2017-1-25 18:15编辑过]

float a[60][2]== 多了一个等号，
再把x[2][17]的类型改为int试试

[此贴子已经被作者于2017-1-25 18:16编辑过]

printf("\n");   
    for(i=0;i<2;i++)
        for(j=0;j<17;j++)
        scanf("%f",&x[i][j]);    //"%d"
        printf("\n");   

float a[60][2]=   //去掉这个float

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

  int commp(const void *a, const void *b)                                
{                                
return ((float *)a)[0] > ((float *)b)[0] ? 1 : -1;                                
}                                
 main()               
{   
    float c[25],a[30][2];     int x[2][17];
    int i,j;
    printf("\n");   
    for(i=0;i<25;i++)
        scanf("%f",&c[i]);
   
    printf("\n");   
    for(i=0;i<2;i++)
        for(j=0;j<17;j++)
        scanf("%d",&x[i][j]);
        printf("\n");  
        
a[30][2]={{c[x[0][2]]-c[x[0][1]]-c[x[0][0]],x[0][2]-x[0][1]-x[0][0]},
{c[x[0][3]]-c[x[0][2]]-c[x[0][1]],x[0][3]-x[0][2]-x[0][1]},
{c[x[0][4]]-c[x[0][3]]-c[x[0][2]],x[0][4]-x[0][3]-x[0][2]},
{c[x[0][5]]-c[x[0][4]]-c[x[0][3]],x[0][5]-x[0][4]-x[0][3]},
{c[x[0][6]]-c[x[0][5]]-c[x[0][4]],x[0][6]-x[0][5]-x[0][4]},
{c[x[0][7]]-c[x[0][6]]-c[x[0][5]],x[0][7]-x[0][6]-x[0][5]},
{c[x[0][8]]-c[x[0][7]]-c[x[0][6]],x[0][8]-x[0][7]-x[0][6]},
{c[x[0][9]]-c[x[0][8]]-c[x[0][7]],x[0][9]-x[0][8]-x[0][7]},
{c[x[0][10]]-c[x[0][9]]-c[x[0][8]],x[0][10]-x[0][9]-x[0][8]},
{c[x[0][11]]-c[x[0][10]]-c[x[0][9]],x[0][11]-x[0][10]-x[0][9]},
{c[x[0][12]]-c[x[0][11]]-c[x[0][10]],x[0][12]-x[0][11]-x[0][10]},
{c[x[0][13]]-c[x[0][12]]-c[x[0][11]],x[0][13]-x[0][12]-x[0][11]},
{c[x[0][14]]-c[x[0][13]]-c[x[0][12]],x[0][14]-x[0][13]-x[0][12]},
{c[x[0][15]]-c[x[0][14]]-c[x[0][13]],x[0][15]-x[0][14]-x[0][13]},
{c[x[0][16]]-c[x[0][15]]-c[x[0][14]],x[0][16]-x[0][15]-x[0][14]},

{c[x[1][2]]-c[x[1][1]]-c[x[1][0]],x[1][2]-x[1][1]-x[1][0]},        
{c[x[1][3]]-c[x[1][2]]-c[x[1][1]],x[1][3]-x[1][2]-x[1][1]},        
{c[x[1][4]]-c[x[1][3]]-c[x[1][2]],x[1][4]-x[1][3]-x[1][2]},        
{c[x[1][5]]-c[x[1][4]]-c[x[1][3]],x[1][5]-x[1][4]-x[1][3]},        
{c[x[1][6]]-c[x[1][5]]-c[x[1][4]],x[1][6]-x[1][5]-x[1][4]},        
{c[x[1][7]]-c[x[1][6]]-c[x[1][5]],x[1][7]-x[1][6]-x[1][5]},        
{c[x[1][8]]-c[x[1][7]]-c[x[1][6]],x[1][8]-x[1][7]-x[1][6]},        
{c[x[1][9]]-c[x[1][8]]-c[x[1][7]],x[1][9]-x[1][8]-x[1][7]},        
{c[x[1][10]]-c[x[1][9]]-c[x[1][8]],x[1][10]-x[1][9]-x[1][8]},        
{c[x[1][11]]-c[x[1][10]]-c[x[1][9]],x[1][11]-x[1][10]-x[1][9]},        
{c[x[1][12]]-c[x[1][11]]-c[x[1][10]],x[1][12]-x[1][11]-x[1][10]},        
{c[x[1][13]]-c[x[1][12]]-c[x[1][11]],x[1][13]-x[1][12]-x[1][11]},        
{c[x[1][14]]-c[x[1][13]]-c[x[1][12]],x[1][14]-x[1][13]-x[1][12]},        
{c[x[1][15]]-c[x[1][14]]-c[x[1][13]],x[1][15]-x[1][14]-x[1][13]},        
{c[x[1][16]]-c[x[1][15]]-c[x[1][14]],x[1][16]-x[1][15]-x[1][14]}};



 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("%f", a[i][0]);                        
if(a[i][1] = a[i+1][1])                        
printf("%f", a[i+1][0]);                        
                        
printf("\n");                        
break;                        
}                        
 }                        
 return 0;   
   
                       
}   



.c(22) : error C2059: syntax error : '{'

[此贴子已经被作者于2017-1-25 18:40编辑过]

还是先计算出来数据，再排序好；