常见的查找算法C语言版本

/*文件命名：search.c

欢迎大家指正

*/

#include <stdio.h>

#include <stdlib.h>

#include <time.h>

#include <string.h>

#define N 10000000

#define STEP 3

#define LOOP 500000

// for string search

#define STR_LEN 10

#define CHAR_SIZE 10

// for hash table

#define HASH_SIZE (N/100+1)

struct node {

char szKeyword[STR_LEN];

struct node *next;

};

int a
;

int g_nMax=0;

char g_szKey
[STR_LEN];

struct node *hashHead[HASH_SIZE];

// 给 qsort 使用

int str_compare(const void *s1, const void *s2)

{

return *(const char *)s1-*(const char *)s2;

}

// String 使用的 binary search

int str_binary_search(int min, int max, char *s)

{

int mid=0,n;

if (min > max) return -1;

mid = min + (max - min) / 2;

n = strcmp(s,g_szKey[mid]);

if (n == 0)

return mid;

else if (n < 0)

return binary_search(min,mid-1,s);

else

return binary_search(mid+1,max,s);

} // int str_binary_search(int min, int max, char *s)

// 数字使用的 binary search

int binary_search(int min, int max, int n)

{

int mid=0;

if (min > max) return -1;

mid = min + (max - min) / 2;

if (a[mid] == n)

return n;

else if (n < a[mid])

return binary_search(min,mid-1,n);

else

return binary_search(mid+1,max,n);

} // int bsearch(int min, int max, int n)

int hash_function(char *s) {

int i,n;

unsigned int sum=0;

if (s == NULL)

return -1;

n = strlen(s);

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

sum = (sum << 7) + s[i];

return sum % HASH_SIZE;

} // end of hash_function

int main(void)

{

time_t t=0;

int i,j,k,n=0;

int nLen=0;

clock_t begin=0,end=0;

char szSearch[STR_LEN];

struct node *ptr=NULL;

////////////////////////////

// Build an array (increasing)

////////////////////////////

time(&t);

srand(t);

for (i=0;i<N;i++) {

a[i] = g_nMax + 1 + (rand()%STEP);

g_nMax = a[i];

} // end of for (i=0;i<N;i++)

n = rand() % (g_nMax + 1);

////////////////////////////

// Sequential search

// find n in the array

////////////////////////////

begin = clock();

for (i=0;i<N;i++) {

if (a[i] == n) {

printf("%d 找到了\n",n);

break;

}

}

if (i == N)

printf("%d 没找到\n",n);

end = clock();

printf("Sequential search \t花费时间=%f\n",(float)(end-begin)/CLOCKS_PER_SEC);

/////////////////////////////

// Binary search

/////////////////////////////

begin = clock();

for (i=0;i<LOOP;i++) {

binary_search(0,N-1,n);

}

end = clock();

printf("Binary search \t\t花费时间=%.8lf\n",(double)(end-begin)/LOOP/CLOCKS_PER_SEC);

/////////////////////////////

// Build random string array

// 建立 N 个 长度 5 ~ 9 的 strings, 存在 g_szKey[i] 里面

/////////////////////////////

for (i=0;i<N;i++) {

// 长度为 5,6,7,8,9

nLen = rand() % 5 + 5; // 5,6,7,8,9

for (j=0;j<nLen;j++)

g_szKey[i][j] = (rand() % CHAR_SIZE) + 'A'; // A,B,C...

g_szKey[i][j] = '\0';

}

// 把 g_szKey 排序排好 (binary search 会用到)

qsort(g_szKey,N,STR_LEN,str_compare);

// Randomly generate szSearch, 产生等等要搜索的 szSearch

nLen = rand() % 5 + 5;

for (i=0;i<nLen;i++)

szSearch[i] = (rand() % CHAR_SIZE) + 'A'; // A,B,C...

szSearch[i] = '\0';

////////////////////////////

// Sequential search

// find szSearch in the array g_szKey

////////////////////////////

begin = clock();

for (i=0;i<N;i++) {

if (strcmp(g_szKey[i],szSearch) == 0) {

printf("%s 找到了\n",szSearch);

break;

}

}

if (i == N)

printf("%s 没找到\n",szSearch);

end = clock();

printf("Sequential search \t花费时间=%f\n",(float)(end-begin)/CLOCKS_PER_SEC);

/////////////////////////////

// Binary search

// find szSearch in the array g_szKey

/////////////////////////////

begin = clock();

for (i=0;i<LOOP;i++) {

str_binary_search(0,N-1,szSearch);

}

end = clock();

printf("Binary search \t\t花费时间=%.8lf\n",(double)(end-begin)/LOOP/CLOCKS_PER_SEC);

/////////////////////////////

// Build hash table

/////////////////////////////

memset(hashHead,0,sizeof(struct node *)*HASH_SIZE);

for (i=0;i<N;i++) { // insert into hash table

n = hash_function(g_szKey[i]);

if ((ptr = (struct node *)malloc(sizeof(struct node))) == NULL) {

printf("Malloc failed in %d\n",__LINE__);

return;

}

strncpy(ptr->szKeyword,g_szKey[i],STR_LEN-1);

ptr->szKeyword[STR_LEN-1] = '\0';

ptr->next = hashHead
;

hashHead
= ptr;

} // end of for (i=0;i<N;i++)

/////////////////////////////

// Hash table search

// find szSearch in the hash table

/////////////////////////////

begin = clock();

for (i=0;i<LOOP;i++) {

n = hash_function(szSearch);

ptr = hashHead
;

while(ptr != NULL) {

if (strcmp(ptr->szKeyword,szSearch) == 0)

break;

ptr = ptr->next;

}

}

end = clock();

printf("Hash table search \t花费时间=%.8lf\n",(double)(end-begin)/LOOP/CLOCKS_PER_SEC);

return 0;

} // end of main()