C 中经典字符串算法实现

 1  1 #define _CRT_SECURE_NO_WARNINGS
 2  2 
 3  3 #include<stdio.h>
 4  4 #include<stdlib.h>
 5  5 #include<string.h>
 6  6 
 7  7 void Upper(char *p)
 8  8 {
 9  9     int len = strlen(p);
10 10     for (int i = 0; i < len - 1; i++)
11 11     {
12 12         if (p[i] >= ‘a‘&&p[i] <= ‘z‘)
13 13         {
14 14             p[i] = p[i] - ‘a‘ + ‘A‘; //p[i] -= 32; 在ASCII表里小写字母的值比对应大写字母的值大32.
15 15         }
16 16     }
17 17 }
18 18 
19 19 void Lower(char *p)
20 20 {
21 21     int len = strlen(p);
22 22     for (int i = 0; i < len - 1; i++)
23 23     {
24 24         if (p[i] >= ‘A‘&&p[i] <= ‘Z‘)
25 25         {
26 26             p[i] = p[i] + ‘a‘ - ‘A‘;//p[i] += 32;
27 27         }
28 28     }
29 29 }
30 30 
31 31 void main()
32 32 {
33 33     char str[128] = "MSpaint";
34 34     puts(str);
35 35 
36 36     Upper(str);
37 37     puts(str);
38 38 
39 39     Lower(str);
40 40     puts(str);
41 41 
42 42     system("pause");
43 43 }

 1 #define _CRT_SECURE_NO_WARNINGS
 2 
 3 #include<stdio.h>
 4 #include<stdlib.h>
 5 #include<string.h>
 6 
 7 void invert(char *p)    
 8 {
 9     int i;
10     char x;
11     int len = strlen(p);
12     for (i = 0; i < len/2; i++)
13     {
14         x = p[i];
15         p[i] = p[len - i - 1];
16         p[len - i - 1] = x;
17     }
18 }
19 
20 void main()
21 {
22     char str[128] = "evil rail tap loop";
23     puts(str);
24 
25     invert(str);
26     puts(str);
27 
28     system("pause");
29 }