bsearch
使用二分查找,查找一个被排序过的数组
依赖头文件
#include <stdlib.h>
void *bsearch(const void *key, const void *base,
size_t nmemb, size_t size,
int (*compar)(const void *, const void *));
描述
key : 指向要查找的元素
base : 指向被查找的数组
nmemb : 被查找数组的大小
size : 被查找数组元素的大小
int (*compar)(const void *, const void *) : 比对的函数
RETURN VALUE
查找到了就返回对应的元素,查找不到就返回NULL
┌──────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────┼───────────────┼─────────┤
│bsearch() │ Thread safety │ MT-Safe │
└──────────┴───────────────┴─────────┘
使用示例:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct mi {
int nr;
char *name;
} months[] = {
{ 1, "jan" }, { 2, "feb" }, { 3, "mar" }, { 4, "apr" },
{ 5, "may" }, { 6, "jun" }, { 7, "jul" }, { 8, "aug" },
{ 9, "sep" }, {10, "oct" }, {11, "nov" }, {12, "dec" }
};
#define nr_of_months (sizeof(months)/sizeof(months[0]))
static int
compmi(const void *m1, const void *m2)
{
struct mi *mi1 = (struct mi *) m1;
struct mi *mi2 = (struct mi *) m2;
return strcmp(mi1->name, mi2->name);
}
int
main(int argc, char **argv)
{
int i;
qsort(months, nr_of_months, sizeof(struct mi), compmi);
for (i = 1; i < argc; i++) {
struct mi key, *res;
key.name = argv[i];
res = bsearch(&key, months, nr_of_months,
sizeof(struct mi), compmi);
if (res == NULL)
printf("'%s': unknown month\n", argv[i]);
else
printf("%s: month #%d\n", res->name, res->nr);c
}
exit(EXIT_SUCCESS);
}
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