1 class Solution {
2 public:
3 int strStr(char *haystack, char *needle) {
4
5 int i = 0 , skip[256];
6 char *str = haystack, *substr = needle;
7 int len_src = strlen(str), len_sub = strlen(substr);
8 // preprocess
9 for (i = 0; i < 256; i++)
10 skip[i] = len_sub;
11 int last = len_sub - 1;
12 for (i = 0; i < last;i++)
13 skip[substr[i]] = last - i;
14 // search
15 int pos = 0, j;
16 while (pos <= len_src-len_sub) {
17 j = last;
18 while (j>=0 && str[pos+j]==substr[j])
19 j--;
20 if (j<0)
21 return pos;
22 pos += skip[str[pos+last]];
23 }
24 return -1;
25 }
26 };
