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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3.  
  4. typedef struct {
  5.     double x;
  6.     double y;
  7. } data2d;
  8.  
  9.  
  10. int
  11. comp (const void *p1, const void *p2)
  12. {
  13.     const data2d d1 = *(const data2d*)p1;
  14.     const data2d d2 = *(const data2d*)p2;
  15.     double x1 = d1.x,y1 = d1.y,x2 = d2.x, y2 = d2.y;
  16.  
  17.     if( x1 < x2 ) return -1;
  18.     if( x1 > x2 ) return 1;
  19.     if( y1 < y2 ) return -1;
  20.     if( y1 > y2 ) return 1;
  21.     return 0;
  22. }
  23.  
  24. int main()
  25. {
  26.  
  27.     int i = 0;
  28.     data2d *xy = calloc(10, sizeof*xy);
  29.  
  30.     xy[0].x = 1.2;      xy[0].y = 1.019;
  31.     xy[1].x = 2.02;     xy[1].y = 33.98;
  32.     xy[2].x = 3.25;     xy[2].y = 321.2;
  33.     xy[3].x = 5.11;      xy[3].y = 105.1;
  34.     xy[4].x = 5.11;     xy[4].y = 78.77;
  35.     xy[5].x = 3.42;     xy[5].y = 658.5;
  36.     xy[6].x = 3.42;     xy[6].y = 688.8;
  37.     xy[7].x = 21.2;     xy[7].y = 1.081;
  38.     xy[8].x = 100.2;    xy[8].y = 132.4;
  39.     xy[9].x = 19.2;     xy[9].y = 1.157;
  40.  
  41.     printf("before qsort()\n");
  42.     printf("==============\n");
  43.     for (i=0; i<10; i++)
  44.         printf("xy[%d].x = %.3f   xy[%d].y = %.3f\n", i, xy[i].x, i, xy[i].y);
  45.  
  46.     qsort(xy, 10, sizeof*xy, comp);
  47.  
  48.     printf("after qsort()\n");
  49.     printf("==============\n");
  50.     for (i=0; i<10; i++)
  51.         printf("xy[%d].x = %.3f   xy[%d].y = %.3f\n", i, xy[i].x, i, xy[i].y);
  52.  
  53.     free(xy);
  54.     return 0; 
  55. }
  56.  
Success #stdin #stdout 0s 1920KB
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Standard input is empty
stdout
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before qsort()
==============
xy[0].x = 1.200   xy[0].y = 1.019
xy[1].x = 2.020   xy[1].y = 33.980
xy[2].x = 3.250   xy[2].y = 321.200
xy[3].x = 5.110   xy[3].y = 105.100
xy[4].x = 5.110   xy[4].y = 78.770
xy[5].x = 3.420   xy[5].y = 658.500
xy[6].x = 3.420   xy[6].y = 688.800
xy[7].x = 21.200   xy[7].y = 1.081
xy[8].x = 100.200   xy[8].y = 132.400
xy[9].x = 19.200   xy[9].y = 1.157
after qsort()
==============
xy[0].x = 1.200   xy[0].y = 1.019
xy[1].x = 2.020   xy[1].y = 33.980
xy[2].x = 3.250   xy[2].y = 321.200
xy[3].x = 3.420   xy[3].y = 658.500
xy[4].x = 3.420   xy[4].y = 688.800
xy[5].x = 5.110   xy[5].y = 78.770
xy[6].x = 5.110   xy[6].y = 105.100
xy[7].x = 19.200   xy[7].y = 1.157
xy[8].x = 21.200   xy[8].y = 1.081
xy[9].x = 100.200   xy[9].y = 132.400
https://ideone.com/EGXyKE
language:
C (gcc 8.3)
created:
12 years ago
visibility:
public

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