字符串倒序查找字串

1. #include.h>
2. #include<string.h>
4. char*myStrrstr(constchar*haystack,constchar*needle);
6. int
7. main(void)
8. {
9. char*s="hello world";
10. char*t="ll";
11. char*r=myStrrstr(s,t);
12. printf(r);
14. return 0;
15. }
17. char*myStrrstr(constchar*haystack,constchar*needle)
18. {
19. unsigned int i;
20. unsigned int hay_len,need_len;
21. constchar*p;
23. if(NULL==haystack||NULL==needle)
24. returnNULL;
27. hay_len=strlen(haystack);
28. need_len=strlen(needle);
30. if(need_len==0)
31. return(char*)haystack;
33. if(hay_len< need_len)
34. returnNULL;
36. p=haystack+hay_len-need_len;
38. while(p>=haystack)
39. {
40. for(i=0;i< need_len;i++)
41. if(p[i]!=needle[i])
42. gotonext;
43. return(char*)p;
45. next:
46. p--;
47. }
49. returnNULL;
50. }