string reverse in C

1:  M#1  
2:  void own_strrev(char *str)  
3:  {  
4:    char *start = str;  
5:    char *end = str + strlen(str) -1;  
6:    char ch;  
7:    printf("Start : %c\tend : %c\n", *start, *end);  
8:    while(end > start)  
9:    {  
10:      ch = *start;  
11:      *start = *end;  
12:      *end = ch;  
13:      start++;  
14:      end--;  
15:    }  
16:  }  
17:  M#2  
18:  char *own_strrev(const char *str)  
19:  {  
20:    int len = strlen(str),i=0;  
21:    char *ptr = malloc(len+1);  
22:    for(i=0,len -=1; len>=0;i++,len--)  
23:    {  
24:      ptr[i] = str[len];  
25:    }  
26:    ptr[i] = '\0';  
27:    return ptr;  
28:  }