在嵌入式开发中，可以使用c标准库自带的库函数，而不用自己去早*，qsort 和bsearch就是其中的两个比较好用的

二分法查找，前提是已经排序好的数据。下面的代码， 如果数据为排序，则要进行排序后，再查找。

/* bsearch example */

#include <stdio.h>      /* printf */

#include <stdlib.h>     /* qsort, bsearch, NULL */

int compareints (const void *a, const void *b)

{

    return ( *(int *)a - * (int *)b );

}

int values[] = { 50, 20, 60, 40, 10, 30 };

int main ()

{

    int *pItem;

    int key = 45;

    qsort (values, 6, sizeof (int), compareints);

    pItem = (int *) bsearch (&key, values, 6, sizeof (int), compareints);

    if (pItem != NULL)

        printf ("%d is in the array.\n", *pItem);

    else

        printf ("%d is not in the array.\n", key);

    return 0;

}

快速排序

#include <stdio.h>

#include <stdlib.h>

int values[] = { 88, 56, 100, 2, 25 };

int cmpfunc (const void *a, const void *b)

{

    return ( *(int *)a - * (int *)b );  //升序

    //return ( *(int *)a - * (int *)b );  //降序

}

int main()

{

    int n;

    printf("排序之前的列表：\n");

    for ( n = 0 ; n < 5; n++ )

    {

        printf("%d ", values[n]);

    }

    qsort(values, 5, sizeof(int), cmpfunc);

    printf("\n排序之后的列表：\n");

    for ( n = 0 ; n < 5; n++ )

    {

        printf("%d ", values[n]);

    }

    return (0);

}

比较函数需要特别注意~~~~

Pointer to a function that compares two elements.

This function is called repeatedly by qsort to compare two elements. It shall follow the following prototype:

int compar (const void* p1, const void* p2);

Taking two pointers as arguments (both converted to const void*). The function defines the order of the elements by returning (in a stable and transitive manner):

For types that can be compared using regular relational operators, a general compar function may look like:

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int compareMyType (const void * a, const void * b)

{

  if ( *(MyType*)a <  *(MyType*)b ) return -1;

  if ( *(MyType*)a == *(MyType*)b ) return 0;

  if ( *(MyType*)a >  *(MyType*)b ) return 1;

}