计算字符串长度和拼接字符串的方法

 1 //strlen - calculate the length of a string//
 2 
 3 #include 
 4 
 5 int strlens(const char *s);
 6 char strcats(char *dest, const char *src);
 7 
 8 #define NUM 100
 9 
10 int main(void)
11 {
12     char c[NUM];
13     char *s;
14     s = c;
15 
16     printf("Please input: ");
17     gets(s);
18 
19     printf("The length of string is %d.\n",strlens(s));
20     return 0;
21 }
22 
23 
24 int strlens(const char *s)
25 {
26     int i;
27 
28     for (i = 0; *s++ != ‘\0‘; i++);
29 
30     return i;
31 }

 1 /* concatenate two strings */
 2 
 3 #include 
 4 
 5 char* strcats(char *dest,const char *src);
 6 
 7 int main(void)
 8 {
 9     char a[100],b[100];
10     char *m,*n;
11     m = a;
12     n = b;
13     printf("Please input: ");
14     gets(m);
15     printf("Please input: ");
16     gets(n);
17 
18     puts(m);
19     puts(n);
20     strcats(m,n);
21     
22     puts(m)    ;
23     
24     return 0;
25 }
26 
27 char* strcats(char *dest,const char *src)
28 {
29     int i = 0;
30     char *ch = dest;
31 
32     while (*ch) {
33         ch++;
34     }
35 
36     while (*ch++ = *src++);
37 
38     return (dest);
39 }

 1 #include 
 2 
 3 char* strcpys(char * dest,const char * src);
 4 
 5 int main(void)
 6 {
 7     char c[100],d[100], *s,*q;
 8     s = c;
 9     q = d;
10     printf("Please input: ");
11     gets(s);
12     printf("Please input: ");
13     gets(q);
14     
15     strcpys(s,q);
16     puts(s);
17 //    puts(q);
18 
19     return 0;
20 }
21 
22 char* strcpys(char * dest,const char * src)
23 {
24     while (*src != ‘\0‘) {
25         *dest++ = *src++;
26     }
27     *dest = ‘\0‘;
28 
29     return dest;
30 
31 }

 1 #include 
 2 
 3 strcmps(char *s, char *t);
 4 
 5 int main(void)
 6 {
 7     int N;
 8     char a[100],b[100],*s,*q;
 9     s = a;
10     q = b;
11 
12     printf("Please input: ");
13     gets(s);
14     printf("Please input: ");
15     gets(q);
16     
17     N = strcmps(s,q);
18     printf("%d\n",N);
19 
20     return 0;
21 }
22 
23 strcmps(char *s, char *t)
24 { 
25     while(*s==*t)
26     {
27         if(*s !=‘\0‘) 
28             return 0;
29         ++s;  ++t;
30     }
31     return (*s - *t);        
32 }