qsort不适用于双数组

Question

我尝试使用qsort对一个double值数组进行排序,但它似乎不起作用.想知道这里出了什么问题？

#include <stdio.h>
#include <stdlib.h>
static double compare (const void * a, const void * b)
{
  if (*(double*)a > *(double*)b) return 1;
  else if (*(double*)a < *(double*)b) return -1;
  else return 0;  
}

int main() {

    int idx;
    double* sum_least_square_err;

    sum_least_square_err = (double*) malloc (2500*2500*sizeof(double));

    sum_least_square_err[0] = 0.642;    
    sum_least_square_err[1] = 0.236;
    sum_least_square_err[2] = 0.946;
    idx = 3;

    qsort(sum_least_square_err, idx, sizeof(sum_least_square_err), compare);

    int i;
    for (i=0; i<idx; i++){
       fprintf(stderr,"sum_least_square_err[%d] = %.3f\n", i, sum_least_square_err[i]);            
    }
    fprintf(stderr,"MAEE = %.3f\n", sum_least_square_err[idx/2]);

    free(sum_least_square_err);
}

---

结果:

sum_least_square_err [0] = 0.642

sum_least_square_err [1] = 0.236

sum_least_square_err [2] = 0.946

MAEE = 0.236

Answer 1

更改:

static double compare (const void * a, const void * b)

至:

static int compare (const void * a, const void * b)

并改变:

qsort(sum_least_square_err, idx, sizeof(sum_least_square_err), compare);

至:

qsort(sum_least_square_err, idx, sizeof(sum_least_square_err[0]), compare);

注意:您应该有关于第一个错误的适当编译器警告 - 您是编译gcc -Wall还是等效,如果是,您是否注意到编译器警告？(如果没有那么请接受提示,让编译器在将来为您捕获这样的问题.)