C語言使用stdlib.h庫函數的二分尋找和快速排序程式

快速排序：

#include <stdlib.h>#include <stdio.h>#include <string.h>#define LENGTH(x) sizeof(x)/sizeof(x[0])/**輸出數組元素*\param arr:指向數組的指標*\param len:數組元素的個數*/void print(char (*arr)[10],int len){    int i;    for (i=0;i<len;i++)    {        printf("%s ",arr[i]);    }    printf("\n");}int main(){    char arr[][10]={"bac","bca","abc","acb","cba","cab"}; /* 定義二維字元數組*/    char *key="bca";/* 要尋找的字串*/    char *ptr=NULL; /* 字元指標*/// 輸出未排序時字元數組的內容    printf("before qsort :");    print(arr,LENGTH(arr));    /* 使用qsort對字元數組排序*/    qsort((void *)arr,LENGTH(arr),sizeof(arr[0]),(int (*)(const void *,const void *))strcmp);    /* 輸出排序後字元數組的內容*/    printf("after qsort :");    print(arr,LENGTH(arr));    /* 採用二分尋找尋找指定字元*/    ptr=(char *)bsearch(key,arr,LENGTH(arr),sizeof(arr[0]),(int (*)(const void *,const void *))strcmp);    if(ptr)    {        /* 找到*/        printf("%s is in the array\n",key);    }    else/* 沒找到*/    {        printf("%s isn't in the array\n",key);    }    return 0;}

二分尋找：

#include<stdlib.h>#include<stdio.h>#define ArrayLen(arr) (sizeof(arr) / sizeof(arr[0]))int numarray[] = {123, 145, 512, 627, 800, 933};int numeric (const int *p1, const int *p2){    return(*p1 - *p2);}int* lookup(int key){//傳回值是指向key的地址     int *itemptr;    // The cast of (int(*)(const void *,const void*)) is needed to avoid a type mismatch error at// compile time    itemptr = (int *)bsearch(&key, numarray, ArrayLen(numarray),\                             sizeof(int), (int(*)(const void *,const void *))numeric);    return (itemptr);}int main(void){int *p = lookup(512);if(NULL != p)printf("找到的key是%d，", *p);printf("key的下標是%d\n", (p - numarray));    return 0;}