c语言 输入若干字符串 用指针和一位数组 冒泡排序 C 语言作业 - 1 - 指针使用与冒泡排序...

上周四 Programming 课程布置了一个作业，要求如下：

Write a C module for sorting string pointer array. And write a test program for string sorting using the module.

大致意思就是对一个字符数组进行排序；比较的方法有两种，一种是基于 ASCII 码的大小，一个是基于整数值的大小；最后用冒泡排序来测试这两种比较方法。

真的是，时隔很久又重新捡起 C 语言啊。

charstrcmp()

该函数是基于 ASCII 码来比较字符串的。一般的字符串比较都是基于这种方法，先比较首字母的 ASCII 码的大小，如果首字母相同再比较第二个字母，以此类推。举例来说：

“april” and “may” -> “may” > “april”

“standard” and “stantalone” -> “standard” > “tandalone” (‘r’>’l’)

因此，这个函数比较好实现：

/*

function charstrcmp(): compare two strings based on ASCII

*/

int charstrcmp(char *s, char *t)

{

int i=0;

while(s[i]!='\0' || t[i]!='\0')

{

if(s[i] > t[i])

{

return 1;

}

else if(s[i] < t[i])

{

return -1;

}

i++;

}

return 0;

}

initstrcmp()

该函数是基于整数值来比较字符串的。这里第一想法是把字符串数字转换成数字，然后进行比较，但是试过之后感觉好麻烦，而且很多报错。后面就按照下面的步骤来进行了，比较简单：

基于正负数的符号比较

如果符合相同，基于长度比较

如果长度相同，基于字符串大小比较

实现如下：

int initstrcmp(char *s, char *t)

{

int i = 0, sign = 1;

// if s or t is negative

if (s[i] != '-' && t[i] == '-') { return 1; }

if (s[i] == '-' && t[i] != '-') { return -1; }

// if s and t are all negative

if (s[i] == '-' && t[i] == '-' ) { sign = -1; }

// compare based on the length of strings

if(strlen(s) > strlen(t)) { return sign; }

if(strlen(s) < strlen(t)) { return -sign; }

// compare based on the value of strings

while(s[i] != '\0' || t[i] != '\0')

{

if(s[i] > t[i]) { return sign; }

else if(s[i] < t[i]) { return -sign; }

i++;

}

return 0;

}

bubble_sort()

该函数是实现基于前两个比较方法的冒泡排序。关于冒泡排序就不多说了，直接看下面代码：

/*

funciton swap(): swap two pointers

*/

void swap(char **s, char **t)

{

char *tmp;

tmp = *s;

*s = *t;

*t = tmp;

tmp = NULL;

}

/*

function bubble_sort(): bubble sort for strings

*/

void bubble_sort(void *str[], int num, int(*compare)(char *, char*))

{

int i, j;

for(i=0; i

{

for(j=0;j

{

// if str[j] > str[j+1], should swap them

if(compare((char *)str[j], (char *)str[j+1]) > 0)

{

// swap

swap(&str[j], &str[j+1]);

}

}

}

}

实现结果

完整代码如下：

#include

#include

/*

function ptint_out(): print out strings

*/

void print_out(char *str[], int num)

{

printf("{ ");

int i;

for(i=0; i

{

printf("%s ", str[i]);

}

printf("}\n");

}

/*

function charstrcmp(): compare two strings based on ASCII

*/

int charstrcmp(char *s, char *t)

{

int i=0;

while(s[i]!='\0' || t[i]!='\0')

{

if(s[i] > t[i])

{

return 1;

}

else if(s[i] < t[i])

{

return -1;

}

i++;

}

return 0;

}

/*

function initstrcmp(): compare two strings based on integer value

*/

int initstrcmp(char *s, char *t)

{

int i = 0, sign = 1;

// if s or t is negative

if (s[i] != '-' && t[i] == '-') { return 1; }

if (s[i] == '-' && t[i] != '-') { return -1; }

// if s and t are all negative, change the sign

if (s[i] == '-' && t[i] == '-' ) { sign = -1; }

// compare based on the length of strings

if(strlen(s) > strlen(t)) { return sign; }

if(strlen(s) < strlen(t)) { return -sign; }

// compare based on the value of strings

while(s[i] != '\0' || t[i] != '\0')

{

if(s[i] > t[i]) { return sign; }

else if(s[i] < t[i]) { return -sign; }

i++;

}

return 0;

}

/*

funciton swap(): swap two pointers

*/

void swap(char **s, char **t)

{

char *tmp;

tmp = *s;

*s = *t;

*t = tmp;

tmp = NULL;

}

/*

function bubble_sort(): bubble sort for strings

*/

void bubble_sort(void *str[], int num, int(*compare)(char *, char*))

{

int i, j;

for(i=0; i

{

for(j=0;j

{

// if str[j] > str[j+1], should swap them

if(compare((char *)str[j], (char *)str[j+1]) > 0)

{

// swap

swap(&str[j], &str[j+1]);

}

}

}

}

/*

test program for the charstrcmp() and initstrcmp()

*/

int main()

{

// test strings

int num=6;

char *str[] = {"3", "27", "123", "5", "9", "1"};

char *str_1[] = {"3", "27", "123", "5", "9", "1"};

printf("\nOriginal strings: \n");

print_out(str, num);

printf("\n============ Sorted Result ============\n");

// compare based on ASCII

bubble_sort(str,num,charstrcmp);

// compare based on Integer Value

bubble_sort(str_1,num,initstrcmp);

printf("\nResult of %s method:\n", "ASCII");

print_out(str,num);

printf("\nResult of %s method:\n", "Integer Value");

print_out(str_1,num);

return 1;

}

运行结果如下：