void qsort(void *base, size_t num, size_t size, int (*compar)(const void*, const void*));
void *bsearch(const void *key, const void *base, size_t num, size_t size, int (*compar)(const void*, const void*));


qsort  对数组进行排序
base 数组，num为数组中元素数量，size为每个数组元素大小，compar为指向比较函数的指针


bsearch  二分查找有序数组
key 关键字
base 数组
num 数组中元素个数
size 每个数组元素的大小
compare  比较函数的指针




#include "stdio.h"
#include "stdlib.h"


int comp(const void* x, const void *y){
  int *ix = (int *)x;
  int *iy = (int *)y;
  if (*ix > *iy)
    return 1;
  else if (*ix == *iy)
    return 0;
  else
    return -1;
}

int main(){
  int nums[] = {1,2,3,9,7,8};
  int num = sizeof(nums) / sizeof(nums[0]);
  printf("num=%d\n",num);
  
  qsort(nums, num, sizeof(int), comp);
  printf("sorted:");
  int i = 0;
  for (i = 0; i < num; i++){
    printf("%d ", nums[i]);
  }
  printf("\n");

  int k = 7;

  int *findedItem = bsearch(&k, nums, num, sizeof(int), comp);

  if (findedItem != NULL){
    printf("%d exist in array \n", *findedItem);
  }else{
    printf("%d not exist in array\n", k);
  }
  
  k = 20;
  findedItem = bsearch(&k, nums, num, sizeof(int), comp);

  if (findedItem != NULL){
    printf("%d exist in array \n", *findedItem);
  }else{
    printf("%d not exist in array\n", k);
  }

  return 0;
}


https://gitee.com/dyyx/hellocode/blob/master/web/tech/c/demo/stdlib/search_sort2.c