习题8-5 使用函数实现字符串部分复制

 1 void strmcpy(char *t, int m, char *s)
 2 {
 3     int len = 0; //计算字符串t的长度
 4     char *p = t;
 5     int i;
 6     while (*p != '\0')
 7     {
 8         len++;
 9         p++;
10     }
11 
12     if (m <= len)
13     {
14         for (i = 0; t[m - 1 + i] != '\0'; i++)
15         {
16             s[i] = t[m - 1 + i];
17         }
18         s[i] = '\0';
19     }
20     else
21     {
22         *s = '\0';
23     }
24 }